1. I've broken two of the mounts. They broke at the bottom of the cheap plastic inserts where the zip tie snakes through. Another friend has had the same experience (he broke 4). Garmin has come out with a new mount which fixes the problem, but my workaround was to glue the two pieces (the cheap plastic "insert" into the rubber mount) with gorilla glue.
2. Yes, definitely. A new 705 would have cost you ~$400.