I can't stand IC70s, I find them terribly uncomfortable. Second only to Merseytravel Pacer seating in the discomfort stakes for me (did a two hour stint on them today and my back is sore!).
Seating is entirely subjective though - what some like, others dislike. I've heard a lot of rave reviews about the seating on Adelates and 175s, whereas I think they are just OK.
Are we talking of first class r standard though? I find that first is like slouching in an armchair, whereas standard promoted a reasonably good posture. With a reasonable level of padding. I found both comfortable, but think the standard class versions would benefit from a headrest, so you can rest your head, and reduce carriage visibility slightly, but not so much to feel claustrophobic