I reckon the sv650 is a perfect learner sportsbike. Not heaps of power (but enough to have a bit of fun) and a relatively flexible frame to tell you what's going on.
Overall I reckon the best bikes to learn on are dirtbikes though (on dirt of course). When you've got less traction learning to deal with a bike wanting to walk out from under you is a necessity. They're also better to learn to do wheelies on I reckon because of the engine configuration and the weight of the things (also handy when you're picking it up off the ground...)
And to all the people who are saying "don't buy a thou", the throttle twists both ways. I'd rather ride a thou around on the road because you don't have to flog it to get around fairly quickly. I'd rather a 600 for trackdays though.
and astrahl, most learners crash (me included in that one). It's part of learning, most of the time it's slow maneuvering and whatnot, or "parking lot crashes". Another reason to learn on the dirt. Dirt doesn't hurt as much to land on as tarmac (I know this from experience!)