I use a Forerunner 935 normally, but it's getting long in the tooth, so I'm not sure I trust the battery for a full Ironman, assuming the worst case scenario (that it takes the full 17 hours to finish, lol).
I JUST got a Descent yesterday, and was considering using it, since it's got a fresh battery, to do my first IM next month. I don't see any posts or Google hits about anyone using one in a full IM length event, just wondering if there's anything I'm not aware of that would make it a bad choice for a triathlon...other than it's as heavy as a brick, lol.