I rode a base model (an 05) quite a few times. I think that it had potential to be a good bike, but the fork was lousy (the 06 fork is better, but still not that great). If you go up to the COMP level, you go to the Tora fork, which is a pretty good fork, and would address most of my complaints with the bike.
I think the COMP is the sweet spot for this model. The Pro goes to the Recon fork, which is stiffer and takes bigger hits but is less plush on the small bumps...so kind of a mixed bag there--I don't think I would want to pay extra for it. The FSR rear suspension works extremely well, so the move to a Fox rear shock does not make a big difference.
More importantly, its only a couple hundred bucks more to go to the full on Sumpjumper FSR from the FSRxc pro, and that bike is a huge step up. The Fox front fork is, IMHO, a totally different class of fork from the Rockshox forks--and you are getting more travel. You would be crazy not to spend the extra $200.
So, yes, it is a great bike, but go with the COMP model, the base and Pro make little sense to me.