I had mine for 11 months and thought mind was ok, but recently the bubbling on the back of the watch started happening.Once the bubbling wears down, it exposes the base metal which then corrodes.
I contacted Garmin and within 2 days of returning the 610 on a warranty return, I received a brand new watch back. The watch back of the replacement is slightly different to the original - I am guessing it was a common fault so they have done something about it. Still really pleased with the watch, and customer service was faultless