4. Way too few doors. It's kind of articulated as per European trains to give low floor access, but it's totally unnecessary given the height of UK platforms.
It's possible to have two doors per section, as Merseyrail* and TfW are doing, and all the Swiss ones do. The choice of one is to be more commensurate with end-doored units for longer journeys/lower loadings. It's a modular platform, you can spec it any way you want - any window can be a door or vice versa. Poland for example has sets (and very nice they are too, though not so accessible) which are fully high-floor with stepped entrances. The Swiss Girunos (a 140mph version) have doors at two floor heights in the wheelchair-accessible coach.
It's not totally unnecessary given the height of UK platforms; they are the only stock that provides for wheelchair access without a ramp, and that should to me be mandatory. Those huge new fleets of 80x (much as I don't dislike them overall) and Aventras (neutral on those, really) with high floors have set acccessibility back over 30 years.
* These are technically Stadler METRO units but use the same basic components, and look like a FLIRT.
5. Ride quality wasn't especially spectacular, on a par with most other newish trains. Was expecting something akin to a turbostar/HST, reality had more in common with Desiro/Civity.
As I said I thought the general feel in Standard is very similar to a 350/1, which is fine by me, I've more than happily done very long journeys on those, including (once) Bletchley to Liverpool and back direct, taking over 4 hours.
Probably the one thing I don't like about them is the pattern on the windows (some sort of mobile phone signal enhancer, I believe) which to me affects the view a bit, but most people don't notice, I expect. It also isn't anywhere near as bad as the distortion you get on 323s. The escape windows are also a bit clunky and I think could have been done better.