I use my 520 on every ride (3 times a week). In the 2 years that I've been using it I think it has frozen twice and I've lost maybe a ride or two, but that's about it. All in all I would say it's been trouble free and I have even recommended them to friends.

I can understand the frustration with them. The 2 times mine froze I got really upset and probably spent 3 times as much time as was probably necessary in order to get it back up and running just because I was so upset and didn't want to RTFM.