After many trips, I think there are only two things required to make these pretty much perfect from a passenger POV.
1. Fix those stupid taps. It's impossible to wash your hands properly.
2. Turn the volume down on the rather piercing door alarms.
Out of interest, do you find the "little boxes" window film annoying, or is it just me?
Other than that I didn't really, as noted in my little review above, find an awful lot to genuinely complain about, though as a self confessed Stadler fan this is no surprise. Certainly far better kit than the CAF DMUs for Northern, and the FISA LEAN seat is almost identical to my beloved Grammers. Pity Northern didn't go Stadler instead, but I think the Welsh will love theirs (again, pity the whole fleet aren't Stadler rather than quite a lot of CAF).
And then there's the low floor thing. That should be mandatory on all future rolling stock - it's not like all the manufacturers don't do it on the mainland. It'll be just as much of a step change (!) as low floor buses were in the 90s - why bother arranging assistance when you can just remove the need for it?
I didn't find the door bleeps that annoying myself, FWIW.