I'd go for a 520. It's not like all the other Garmins aren't still buggy. I don't think I've ever seen a Garmin firmware release that while fixing some things didn't break other things. In my experience, for any Garmin product, there's usually an optimum firmware rev, usually several versions removed from the final one, depending on how you use the device.

Buying and using a new Garmin is always an adventure.