I have an 03 ST4S which came with a non-gel seat. The newer ST4 & ST3 have a slightly different seat which you can tell easily by a more pronounced lip at the front of the pillion seat to stop the pillion sliding forward.
Anyway, yes we brought a genuine Gel seat and it is superb. The riders seat seems a little wider, the pillion bit is more pronounced, and the wife no longer slides forweard to join me up the front on downhill heavy braking (so my nuts are once again pink & not black
)
One thing though. The catalogue shows a different seat with a tubular storage thing in its base. The new one is not like that, and actually has a U lock instead.
Money well spent if you ask me
[Edited on 26-4-2005 by John W]