I'm a big fan but I can see why some may find them hard.
What I don't get is why there aren't more seats with a thin, supportive back (for good posture and legroom) and a soft, comfortable base. This is the case on the Grammer E3000 Desiro seat (which draws very few complaints, though I think the odd person on here doesn't like them) and more recently the TfW Fainsa Sophia, which is totally different in comfort from all the other implementations of that seat, seeming to entirely lack the metal bar often cited. (I don't like it as much as the new Pendolino seat, but despite generally disliking Sophias, I'd put the TfW version as my second favourite of the new generation seats, and probably the "contoured ironing board" used by Northern as the third).
The particularly silly FISA LEAN seat appears to do that the wrong way round, at least on the Class 196 where the legroom is terrible and the base rock hard. I'm so glad Northern didn't fit these in the 195s, the legroom in the airline seats which is already a bit tight would have made them the same as a 153, only really suitable for small children. I wonder if realising this and thus using a version of the Fainsa Comrail "ironing board" but with a thicker base was why they changed?
FWIW I recently tried the "First Class" version of the LEAN on SWR, intending to pay for Weekend First as Standard was heaving, but was pleased not to be charged (guard didn't bother coming round) as it wasn't particularly good and the thick back meant poor legroom for First Class. Not a great seat, so I don't hold out much hope for the 810s being very comfortable - I expect poor legroom certainly