Ninja 500R is what I have my eye on - but we'll see what comes up on Craigslist. I want a used bike for my first bike...i am quite sure I will lay it down and have some st00pid moments on it - so used is probably my best bet!
Everyone I've talked to says the 250 IS a great great bike to start on - but after 2-3 months, you begin to feel like it's just not enough. But, go with a 500 at the start and you will be happier for a lot longer.