How much of The Underground have you used?

I have covered the entire length of the Bakerloo, Piccadilly and Central lines as a driver. Including Ongar and Aldwych. Although I never drove the Epping/Ongar shuttles, only observed while training.
I would never have had any reason to go to the far extremities of those lines if it werent for my job.

Been everywhere many times over, although only been to Amersham / Chesham a handful of times. Went to Aldwych / Ongar when they were open as part of the Underground. Only been to Heathrow Terminal 5 once.

Never been employed by any railway.

Covered the entire Underground and BR passenger network in my student days (except a few Parliamentary services not shown on Tube maps or the BR timetable map) This included Ongar, Aldwych, and Croxley Green, and also the Woodgrange Park - Forest Gate link and the Kentish Town - Upper Holloway connection, but not the South Acton shuttle (I'm not that old) or the South Tottenham curves (I haven't yet managed to stir myself that early on a Saturday morning!)

However, there are many non-passenger links I have not done, such as the Kennington, Euston, and Kings Cross loops - although I have been to Northumberland Park depot

Added Watford North Curve a few years ago, and other new lines in London as they have opened, although there are a number of recently-opened lines outside London still on my bucket list (the closest to London being Aylesbury Vale Parkway, the new curve at Bicester, and the Kettering - Corby - Melton Mowbray line).

So, everything except

Met Line: Moor Park - Watford
District: Barking - Upminster
Northern: Camden Town - Edgware, Kentish Town - High Barnet/Mill Hill East, South Wimbledon - Morden
Central: North of Stratford

AFAIK the only sections I haven't been on are:
*Kennington to Waterloo
*Hampstead to Edgware
*Ruislip Manor to Uxbridge.
*North Acton to Ealing Broadway
*Theydon Bois to Epping
*Woodford to Leytonstone via Hainault
*Queens Park to Paddington
*Vauxhall to Brixton
*Tottenham Hale to Walthamstow Central
*Chalfont and Latimer to Amersham

I may add more later. I've completed the DLR and done a lot of LO.

Although I'm now staff, the vast majority of my coverage was done before that was the case.

I've managed to tick off every 'regular' part of the network (including Ongar and Aldwych, courtesy the parents at a very, very young age...), as well as the likes of the Kennington loop, Watford North curve (both ways), West Ham siding and the various moves on and off of the Piccadilly/District fast/local lines.Edit:I also did Charing Cross and Shoreditch prior to their abandonment.

Since joining the company I've ticked off numerous more sidings, reversing points and depots, although I couldn't be specific as it's not the sort of thing I keep track of.

Quite happy to stick with the achievement of getting off and having a look around all 270 current stations as part of my hunt for the 'Labyrinth' artworks.

The link between Ruislip Gardens Depot and the Met...
The Diveunder at Neasden
Rickmansworth North Sidings
The bay at Rickmansworth
Watford North curve

Also I have not been employed by LT...

I've never been TfL staff, but I have travelled on every LU, LO, DLR and TfL rail line shown on the map, and I have been to or through every current station - mainly photographing for the quiz. The last to be completed was the Hertford East branch.

I've entered and/or exited at every DLR station including old and new Stratford, South Quay, Tower Gateway and Pudding Mill Lane stations, but not the original Island Gardens or Mudchute, which I never got to travel to. I'm fairly certain I've used all of them for purposes other than photographing them as well.

I've stood on at least one platform at every current LU station, the last one I'm fairly certain was Hounslow East. I've exited and/or entered at nearly all if them, possibly even all, but I'm not confident of that. I'm quite far from having used every station for purposes other than photographing the station, although I ticket Mansion House off that list this week.

For LO, I've not stood on the platform at Theobalds Grove-Southbury or Stoke Newington, and I'm not sure about Wood Street, Crouch Hill or Carpenders Park. I've entered and/or exited at every North, West, East and South London Line station, all three on the Romford-Upminster, every terminus, Upper Holloway, Goblin stations east of Blackhorse Road, West Anglia stations south of Walthamstow Central, Seven Sisters, Highhams Park, White Hart Lane, Bush Hill Park and Edmonton Green.

I've stood on at least one platform at every TfL Rail station (although some only before it was TfL Rail) and have entered and/or exited at all of them except Shenfield.

I've also done Charring Cross Jubilee, Watford north curve and Seven Sisters-Northumberland Park Depot (twice), the Vic-Picc connection and St Mary's Curve, Battersea Park (twice unscheduled). I think I went to the original Shoreditch but I'm not sure of that, I did do the North Woolwich branch all the way. Aldwych and Epping-Ongar are still on my to-do list.

Ha! It wouldn't surprise me - though I am assured that they were for legitimate travel purposes, something I don't doubt as my parents aren't into their trains at all... 

Personally, I'd suggest travelling to the terminus and getting off the train there and spend some time looking round the station - how long depends on the station Epping on a sunny summer's day is very pretty, Upminster doesn't have anywhere near as much going for it imho). Then taking the train back but looking at a few interesting stations on your way back.
If architecture is your thing, then on the eastern end of the Central for example Loughton is a fine art deco station that is worth a look around, including the ticket hall, Gants Hill platform level is a must visit and Mile End platforms are a great example of how a suspended ceiling is not always an improvement.
For the east end of the District I'd suggest Upminster Bridge ticket hall, East Ham (have a good look around), Bow Road (half open, half sub-surface platforms) and Stepney Green (feels quite original).
On the DLR the new Pudding Mill Lane station is worth visiting for the scale, and Devons Road is probably the best example of a first generation station still, Canary Wharf (again for scale) and Cyprus for how it's integrated with the road layout built at the same time.

Not forgetting those stations on the top end of the Piccadilly Line

Absolutely, I just chose not to do a detailed list of all architecturally interesting stations on the Combine, just my pick of those east of Zone 1 on the District and Central lines.

I feel sure that I've been on all sections of line that are open to passengers, including the North Curve. Admittedly only rarely to Elephant and castle (Bakerloo) Brixton and Walthamstow Central (Victoria), and not to Chesham since the 2-9 ODTC's were killed off.

For Watford Junction I think its only been on an Overground train. I recall making a point of travelling on one of the 52 trailers on the Bakerloo Line just before they were withdrawn. The significance of that is that they went in 1972, when I was just 12!, and I travelled alone. Just wish I'd taken the family super 8 film camera with me!!!

I've also been on all the DLR and Tramlink, albeit only rarely to Beckenham Junction. I've not yet been to Wimbledon since the second platform opened... every time I think I will have some free time other people (family members) keep finding things for me to do.

I've also been on the ELL, NLL, WLL, Goblin and Romford-Upminster in their incarnations as part of the Overground network, but not much of the rest of the Overground.

Simon

I have worked on every station on the Underground with the exception of Heathrow Terminal 5. This has been the result of various jobs with the firm and afterwards.

This includes lots of disused areas at Embankment, Charing Cross, Euston, Holborn, Oxford Circus, Baker Street and Liverpool Street amongst others.

More recently this was extended to the vent shafts on the Victoria line.

All in all the Tube is a fascinating place.