1. First off I think the seat is much more comfortable than a traditional sportbike for 2 reasons. There is slightly more padding on the stock Buell seat than other sport bikes, also since the fuel is in the frame the airbox is a shorter length between the handle bars and the seat so when cruising on long rides you can sit in a more upright position. If you still need to tuck into the windscreen to take a corner hard it's very easy to change positions.
2. I bought the XB12R straight out of the box. I never had an XB9 but after riding my 12 for a couple months and then getting on my friends 9 I'm SOOOOOOOOOO glad I bought the 12. In my opinion the 12 screams in comparison to the 9 but I have always been a torque and speed junky.
Hope this helps. Also check out this page to see just how much you can do to these babies.
New Bueller Info Page