From what i can discern - the biggest issues here seem to be the following:
1. Slower delivery of completed trains
2. Greater amount of teething issues with the trains than foreseen - taking longer to fix
3. Crewing issues - not having enough drivers trained in electric mode etc/ not enough train managers causing 5 cars out of a 10 car set to be locked out.
4. HST's, Turbo's and 180's being promised to other operators way too early. This should have been dependent on issues 1 and 2 reaching a satisfactory service level.
The secondary issues seem to revolve around perceived comfort levels and concern that some former 8 coach HST diagrams will now be covered by 5-car trains with less seats.
And with regards to journey times - there were promises of substantial time savings -up to 14 minutes IIRC. What is not clear is whether there we will see anymore than a few minutes shaved off between Paddington and Bristol, and Paddington to Cornwall by virtue of the superior electric performance.
Of course it would be nice to have faster journeys - but it isn't the be all and end all. A slightly slower but punctual service - that has enough seats - is better than one that promises quicker journeys but is frequently late and formed of fewer coaches than expected.
All this is having an impact on capacity - fewer seats than before. The question is how long is it likely to be before there are enough 800's delivered and running reliably enough to resolve this?
Re your point 4, the 180s' lease expired at the end of 2016 - six months before a single IET was due to have entered traffic, even on the original schedule. Grand Central agreed to a 12-month extension. The DfT did not give GWR a choice about holding on to HSTs to provide some margin of cover during the transition. Transfers of Turbos from the Thames Valley to the Bristol area have been slower than planned.
As has been noted in threads on this forum over many years, there are quite a number of GWR services where a five-car IET replacing an HST is simply a non-issue, where HSTs were being used due to the lack of anything else more appropriate to the number of passengers actually travelling, or to to fill in time between longer runs by taking an off-peak trip out to Oxford and back to Paddington, and so on.
The new GWR timetable, with reduced journey times, will not be introduced for another 12 months, so maybe you might actually give GWR a break until that timetable and new sectional running times for IETs are actually in place.
How on earth you can claim there are fewer seats, I have no idea. On the Cotswold Line, 250-seat 166s and 280-seat 180s have been almost eliminated now as a result of the use of 326-seat IETs, while every service on the line where a nine-car IET has replaced an HST has several dozen more seats. And that's just one corner of GWR-land.
I think many less-educated folk use 'regularly' when they mean 'frequently'. The discussion about short-forming has been about how frequently it has been the case that trains are sent out short-formed.
Not many times, as a percentage, but a significant percentage, was my impression of the evidence presented so far.
What evidence? Where are the figures? If it is regular, routine, frequent or any other word you care to choose, then it should be a piece of cake to demonstrate this with some hard numbers.
It would be fairly pointless anyone trying to compile statistics at your invitation, as you seem more interested in patterns than outcomes. It could be 10-30% each day but if occurring in a random pattern, for different reasons, without being deliberate, it would seem to avoid your idea of regular or routine. Even if the cover - a function of both the new and old fleet is to some degree in their control.
I have never subscribed to the 'better half than none' idea. If London - Liverpool ran at a 2% cancellation rate last month then a 98% success rate should be a perfectly reasonable benchmark for getting both halves of the train out.
If people are going to claim that something is routine or regular, then I see no reason at all why they should not provide some evidence, instead of simply asserting it.
Where are all the people who banged on about cancellations due to crewing issues earlier in the year? They wouldn't listen to explanations about the delays to crew training, that GWR actually had a record number of drivers on its books, and so on. Now that training has pretty much caught up, such cancellations have all but disappeared, as have all the posts about them.
As someone who for the best part of two decades has experienced the effects of occasional short-forming on Oxford and Cotswold services so other routes can have an HST, my tolerance level for people droning on about shortforming as though this is some entirely new state of affairs is not great. And I know all about the outcomes on occasions when a two-car Turbo has replaced an HST, thanks.
No one is saying short-forming is a wonderful thing - but it happens on occasion, just like motorways clog up for mile after mile on occasion. If only life was a model of perfection and every train on the network worked like a charm 24/7. But they don't - stuff happens.
And stuff has happened when it has come to the entry into service of the IETs - something that is a matter of fact - just as it did with the not exactly perfect introduction of HSTs in the 1970s.