I'm on one now (for the first time) and I have some thoughts.
First impressions were excellent. The interior materials and lighting give, in my opinion, a really classy and modern appearance without feeling overly harsh (I think this is my favourite interior "ambience" in the UK aside from perhaps the TPE 397). The windows are large and the seats line up with them properly. There are well-positioned USB and plug sockets which you can actually see from your seat (take note, IET designers), as well as coat hooks, massive overhead luggage racks, and plenty of PIS screens. They also accelerate quickly and aren't too loud (they sound, unsurprisingly, identical to 195s). Only obvious issue is the PIS wasn't actually working, but faulty PIS is quite common anyway.
The real disappointment is the seats themselves. Aside from the limited legroom by the standards of modern builds, they have a strange curvy shape that digs into my back unless I sit bolt upright, but I can't comfortably sit bolt upright as the headrest is too low and digs into my shoulders. They've also committed an annoying faux pas I thought we'd finally seen the back of: having seat-back tables which are too small to properly use a laptop on!
If they'd just gone with the same seats as Northern, I'd be calling these a massively improved 195. As it is, I'd much rather do a long journey on a 195 or even a 172 than one of these. Hopefully these seats will "wear in" as suggested above and become more comfortable (though there's no solving the small tables and low headrest) as they are, in my opinion, a massive let-down to an otherwise very good piece of rolling stock design.