My first 10 hours or so on a motorcycle were on a Honda Hornet (a sporty 600 cc street bike with 102 hp). I liked its power, but I read about how nice and easy the Ninja 250R is to ride, and considering how cheap it is, I ended up buying the it.
The only thing at the moment I'd want a bigger bike for, is more of an engine roar. But the sports exhaust I'm getting next week for my 250R will hopefully fix that.
I'm satisfied with the 250R's power. I've only got about 2800 km under my belt with mine, and there's still much to learn for me. Maybe in a few years I'll upgrade, but before I do that I've got to buy a car for the winter seasons.