The GTA seats are fantastic imho, slighty firmer seats actually provides the best long journey comfort and I can vouch for that having done many long journeys in it.
With many other cars my back would be aching after 2hrs or so..
They have adjustable height and wide range of lumbar support.
The slide out bits can be inconvenient if your have short legs I guess and maybe could do with the side bolsters being slightly tighter like the GTs leather seats which imho are the best seats Alfa ever made.
RE ride comfort, the GTA was actually more comfortable than my previous 2.0L 156 with the sports suspension, as well as handling an awful lot better.
Both are rubbish over really bad roads though, they dont have the suspension travel
For city driving, motorway, any smooth roads (no matter how windy), and track use the standard suspension is very good.
It cant cope with well with sudden sharp bumps though so on poor very bumpy b roads you might actually be quicker in a Ford Focus since you would have to back off to avoid bottoming out.
Because of the number for track days I do I did replace the suspension with an Autodelta adjustable damper coilover kit which was really excellent (Sportline Corse).
Depending on the spring rate you choose when purchasing I found that this will actually improve comfort as well as flat-out out handling.