I've been running a NR Mini-Newt, and while it was pricey ($100), it's adequate for the city commute I do and runs for days without a recharge. If I was to do it again, I would probably get something with at least 750 lumens, though. The mini-newt doesn't keep up with a good rolling pace.

I really want to take the jump and get the dynahub, but I don't have the cash for that right now.