For the price, it's worth every cent. If you're doing a fair amount of cycling, having your Garmin mounted directly in front of you, instead of on your wrist, is much better. Very easy to mount, and enables very quick interchanges between the bike and putting the 310XT on your wrist for the run.
Only complaint would be that it does make the watch sit about 5mm higher on your wrist, due to the new quick-release baseplate. But you get used to it... just looks a bit weirder at first.