I've been running an Itronics ITB-100HD for about a year now and have been quite pleased. It's not overwhelmingly fantastic, but does a solid job of reliably recording good video, and it hasn't succumbed to some of the overheating issues that I know have plagued some of the competing Blackvues.
Whatever route you go, I'd encourage checking out
www.dashcamtalk.com. Lots of good reviews, comparisons, and things you should know about a variety of different cameras. Their forums are also a great resource - both from a general support perspective as well as from a firmware hacking perspective.