is the s stock already broken?

On what do you base this "S Stock are already broken" premise? They're not broken and they're replacing trains that, having served with distinction, whither and fade well before the timescale suggested. When will everybody realIse that the A Stock are not fit for purpose going forward.

What also must be remembered that these have been built with durability in mind, as opposed to, 'get the A Stock off the rails as quick as is possible, and I don't care if one bursts into flames from time to time.'

As for comfort, I can't say I noticed much in the way of difference.

The bendy bus comparison is totally irrelevant.

The S8s are a bit longer than A stock. This is to increase capacity. Then by adding the walkthrough facility increases capacity, as it is easier to move down the train and find a space. Whereas with a bendy bus, they have replaced double deckers and become significantly longer. Some routes have had to be cut short - if that's because of tight turns, that's not the issue here, as the car length isn't particularly longer. It isn't a question of length vs passenger density that you get with double deck or bendy bus.

Or think of it this way. With an A stock, you have the space between the cars (supposed to be) inaccessible. What you're basically doing is chopping off the ends and adding a gangway in. Nothing at all like the bendy bus scenario!

S stock are that little bit longer, and it is a simple matter of extending the platforms a bit. Passenger numbers are increasing and the extra train length is needed to compensate for this, as well as a rise in frequency to handle the extra passengers.

Take a look at the Bayswater area. They are some very short platforms round that side of the Circle, and can't even fit a D stock. There's no point in just making 6 car S stock for this. Extending the platforms means you can get extra passengers on the same train, and THEN if you increase tph you get even more of a capacity increase. There's only so many trains you can shove down the tracks, even with CityFlo 650, especially when you consider Praed St. junction, Earl's Court triangle, Minories Junction and Aldgate Junction. You have several lines merging here.

Replacing the A stock also enables modern traction systems to be employed. These have greater efficiency, and if you look at the S-stock's acceleration as a whole, is significantly higher than A C or D stocks. This will allow trains to leave stations quicker. I assume the safety distance for CityFlo will be about 80m, the same as the Jubilee. This would allow the two trains in the same platform scenario you can get with the Victoria Line signalling. You can't do that with tripcock signalling, and the old DC traction systems are rather too crude to work with moving-block ATC.

The Chesham situation is quite simple. You may lose some operational flexibility by losing the bay, but you've got an instant doubling of capacity to/from the station just by the introduction of all-day through services. Having been there off-peak it isn't that huge a demand, but it also makes life simpler for travellers. The bay does immunise the service against almost all main line problems (the points at Chalfont are the only potential mainline ballsup that could knock the service on it) but it is less useful for people travelling into London! If the Met mainline is up the swanney, there's not really much point in taking people to Chalfont, other than for a useful local service, which I bet is also covered by a bus.

You have to look at it on a whole. You might like the A stock - I do too - but it's time is up and it doesn't suit the modern railway.

Like cso said, you have to consider more than just the Amersham commuter. I recall reading that trains effectively fill at Amersham in the peaks. Well, the new trains gain capacity. It may leave a few more people standing but it means that people will be waiting less time for a train as you can fit more people on! The far higher acceleration once CityFlo 650 and the power upgrades are in place will really really be useful for the stopping services.

By adding stops off-peak, you increase the frequency of trains stopping at a station, improving the service available to customers. By increasing the capacity of the trains, and the service overall, you can shift more people. It may prove unnecessary and like MetControl said you can't see how a timetable will work unless you try it out on the real railway! You can play toy trains all day if you want, but toy people won't have dynamic loadings like the way real people do...

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What is the Pinner South / Pinner North tph roughly?

I'd have gussed 6tph each way, but could be wrong?

Also don't forget about accessibility! I saw someone get on at Kings Cross onto the S stock and rode it, but had to change to an A stock at Harrow... it wasn't the best of sights, 2 strangers having to heave him up the step!

Unfortunately, as good as the A stock are, they have issues with space, accessibility, and giving information (maybe on the last one the Underground goes too far, but still!) - plus any longer and the bathtub curve will be rearing its ugly head, with rising fares just to keep these museum pieces (as they will be) on the track!

Well said, unfortunately the Met management don't see it that way and seem to concede when anyone moans about the train service, or as they see it, a lack of it. The Pinner lot are in such a hurry to get to/from London they have to have a train every 7.5 minutes instead of 10!
Hopefully the timetable at the end of the year will be a failure and we can get back to running a proper Met timetable.

What are the long term plans for when the S stock is totally in service for the Met timetable; is the frequency of all services still going to be increased to keep seats/h the same, or has this now been abandoned?

the same kind of failure as you predicted for the new circle pattern in Dec 2009 ?

Or did that turn out 'not so bad' in the end?