I have just replaced the stock seat on my '04 RS with the stock seat from a Sprint RS.

(The original had torn at the front top, just wear & tear.)
I find it perfectly comfortable for a 350 mile day, not bad at all for 550 miles, but horribly uncomfortable after 1000 miles in a day.
I have not had a pillion on a regular basis since I got this bike, so I can't really speak to that issue.
Cheers,
-Kit