I have an '04 Pista that I love. It handles great and I have ridden it fairly long distances. The longest was a 50 mile ride and it was deffinately fine for that long of a ride. Otherwise it has served me well for alot of city miles.
The only downsides I see are that the current bike ('08) jumped in price and looks to have downgraded the componets (at least compared to what my '04 came with). Also, I don't like the fact that it has a 1" threadless headset. Tough to replace with anything midrange. The choices are either low end or something like a King or IRD. Nothing really in the mid range (as far as I know) Maybe the newer ones have a 1 -1/8" headset now, though.
Very few stock parts left on it now, but I do like the frame. Great handling/ride/weight. The only thing I would really consder swaping it out for would be a Bareknuckle.
I don't have any experience w/ the Steamroller.