Had a short experience too on TK1873 IST-MXP in J last November that is normally served by A321 and randomly A330, with one day notice the flight it was changed with ex Aeroflot A350. Same as already mentioned I liked the wide seat, I'm not not a fan of doors but this just my personal taste, sure the IFE system is underwhelming vs TK standard, short selection of movies, no live TV, no games, no maps, in case of long flight better to consider your own alternatives. Cabin ambiance and colors a bit dull/boring, plenty of storage, seat cabinet for jacket nice to see but probably mostly useless, anyway here always YMMV.

On the return TK1876 ten days later I also had the chance to try the B787 (here normally is A330 and A321, it was changed to 787 only that specific day few weeks before the trip) which I also liked, while I'm definitely not a big guy I have to agree the lack of space especially at shoulder level due to the hard seat shell.