I'm sick of people hating on small bikes. People are always talking about how a bike "feels" too slow. Here's a little reality check:
Kawasaki Ninja 250r 0-60: 5.75 1/4 mile: 14.6
2002 Subaru Impreza WRX 0-60: 5.7 1/4 mile: 14.4
1999 Ford Mustang GT 0-60: 5.5 1/4 mile: 14.1
2003 Nissan 350z 0-60: 5.4 1/4 mile: 14.1
1998 BMW M3 Sedan 0-60: 5.5 1/4 mile: 14.0
and something from the category you'll spend most of your time dodging,
2003 Hummer H2 0-60: 10.7 1/4 mile: 17.6
That wimply little beginner bike has some pretty sporting competition down at the drag strip. Sure there are much faster bikes, but anybody saying they _need_ more better be carrying a weeks worth of stuff in hardbags and have a fat girlfriend.
Realistically, if you're doing highway hauls (up the coq or to Squamish) then maybe you need to upgrade to the Ninja 500 for its 224kph top speed (GS500 tops out at 160 kph, like the zzr250, although it runs the quarter mile about a second faster than the 250). The slightly bigger Ninja has acceleration on par with a late-model Dodge Viper, and enough gusto to get you up the hills at high speeds without sweating too much.
The major justification I see people give for riding a larger bike is that they have to shift too much on the small bikes. This bugs the hell out of me - why don't they just buy a scooter, or hell, give up and get in a car and get that cellphone out?
I admit that I'm choked that there aren't any modern options - I'd kill for a fuel-injected 400cc bike with modern brakes and suspension and stiffer lighter frame, but it seems like it'll never happen in North America. Man, imagine it though - Yamaha has a 500cc snowmobile engine (based on the YZ250F mill) making 80 hp and about 49 lb/ft with sweet fuel injection that would make a monster small bike.
Anyways. I'm big on small engines. Hoping to get my own 250 next. Then someday I might replace the XS with a modern 800 for touring 2up - but the real fun starts under 400 pounds, with the kind of power that power that lets you THRASH the bike without getting too reckless.