Agree with the divider and "coffin" sides the latest seat feels smaller -- I'm not sure how much smaller it actually is but boxing in the sides doesn't help.

My biggest peeve and I'm not sure if it's a "new seat issue" or an "Airbus issue" but on the 321 in 2A I cannot fit my laptop bag/backpack under the seat in front of me -- there's an inch in and a half to two inches less vertical clearance than every other aircraft in the UA fleet (there are some 737s where it's "close" but with a little persuasion I can get it in there far enough to satisfy both myself and the FAs it's good; every other aircraft type it goes painlessly) -- this is annoying enough that I'm booking away from that AC type when possible. (Not quite to the "I'll just drive instead" levels of a CRJ200 but close) -- I want my bag to be accessible to me, particularly in a window where between not wanting to annoy the aisle passenger & the whims of the captain's seat belt sign finger mean when it gets in a bin I may not be getting to it during the flight.

One of my first flights with the latest seats there was a random semi-circle grove carved into the IFE display on both 2A and 2B which the pax next to me were speculating as to the source of -- until meal service when we realized that with the pax in front reclined the grove perfectly aligns with the sweep of the tray table while swinging it out to deploy... I had to apply slight forward pressure to the seat in front to get mine out... Not sure if there's actually less usable pitch but that certainly gives the impression that there's less clearance to the seat in front.