Oh yeah, if you go to the AHRMA (
http://www.ahrma.org) vintage races you'll often see out on the track these wizened old guys in their late 60s and into their 70s who happen to be former AMA Grand National champions. If you are on the track at the same time your usual view of them is watching the back of their bike disappear into the distance ahead of you.
Comfort. Think about it. I've been roadracing since 1977, with clip-on bar equipped cafe racers for 3-4 years before that time. I now find (btw I'm 53) that the pressure on the palms of my hands when I ride a bike with low bars makes my hands numb in 10-15 minutes. There aren't as many "standard" bikes as there once were, but the quasi-dual purpose street bikes (really street bikes, but with faux-dirt bike styling) are about as close as you can get these days to a standard with "upright" riding position, while still avoiding the bulk of a full-boat tourer.
Bikes like the 650 Suzuki and Kawasaki twins or the 1000cc Suzuki V-strom make great all-arounders. You can go down gentle dirt roads, do some moderate touring, and rail through the corners. You won't be as good as on something designed for a single purpose, but I've heard from a number of people (especially about the DL650/1000 Suzuki) that they can't imagine ever going back to the more focused bike they used to have.
If you are looking for a track-day street bike where you'll mostly be putting in 20 minute sessions, then the low road-race position is fine. But they really aren't meant for general rding, though I'll admit that the engines are way more tractable and powerful than the race bikes of 15 years ago.
But for a newbie rider, I think something in the 500-650cc range should serve you well. Back when I started riding a 500 was a big bike, and everyone started off on 50/90cc bikes. Nowadays, new riders seem to go out and buy a 145 mph sporting 600 to learn on, which doesn't make a lot of sense to me.
cheers,
Michael