Good points, all. Four-strokes definitely have the 'smooth power delivery' appeal. I like a good 4-stroke as much as the next person. However...
From comments that my buddy has made to me about the RGV250's (he's had 'em all... TZR, RGV, NSR.. I'm jealous as h e l l!), you couldn't have picked a worse 2-stroke to lope around on on the streets. NO bottom end power... even by two-stroke standards... all top end, and very peaky... track oriented. I think they're great bikes, if wrung hard. TZR's have MUCH better 'around-town' riding power, I have one... it's -still- kind of weak below about 5.5~6K, but not un-ridable... they sign off earlier than all the others though and have less peak power and are hard to hop-up, it's a compromize. My RZ350, on the other hand, has pretty good torque for a two-stroke and you can lope around on it pretty well (yep, I'm a two-stroke nut) ... kits exist to punch 'em out to close to 500cc, more if you go to Banshee cylinders (no powervalves though). WooHoo!.. next project!
And you're right, the size of the guy riding does matter. I'm on the ragged edge of being the 'right size' (170lbs) for my TZR250, but it still manages to haul me around pretty good. It's like the other guy was saying.. you really have to stay on top of the powerband, shift up and down like crazy, and you'll be just fine. It doesn't take much to kick a little 2-stroke down a couple of gears and whack the go handle! wooHoo! love the powerband!
Let's not forget that these are little 250's after all! If you bought/ride one b/c you want to be the drag-race king on the street, you bought the wrong bike!

That said, there's few/no typical cars that'll match you off the line... just don't mess with 600's light-to-light!
I also agree with whoever it was above wishing someone would make a modern 500cc 2st... they CAN be made to be clean.. Honda has the technology.. there's an article on this very site that details it. Aprilia's F.I. is on the right track... it's possible, it's just a matter of demand/economics.
To Aprilia: I would sell everything to get a new, modern, clean 500cc stroker!!... dunno if enough people agree w/me though. I still think that if one company would do it, and not charge Bimota V-Due money for it, that the press would get out, and throngs of people would convert... it's -that- much fun to ride one.
This concludes my 'standard rant/babble' about two-strokes on this website for I say the same things (or nearly so!) every time two-strokes become the subject matter! lol!
-James