I found the seat on my 08 GSA very hard and uncomfortable, a 400 mile tank range ruined by a 100 mile seat range! I am 5ft 11 and 75kg. I had Tony Archer rework front and back seats. Front lowered by an inch and re-upholstered in memory foam, back was re-upholstered in memory foam to allow a pillion to sink in a little more and not to slide around as much. Both were finished in black non slip material rather than the the stock black and grey. Looks so much nicer (to me).
Turn round was about a week and I have no idea how much it cost as it was ages ago, I dont remember being horrified though!
This has transformed the bike, the only downside is the knee angle is now a little tighter, I could fit lower pegs but I am used to it now even with my worn out knees.