It should just work, if you're having to improvise cables etc then go for a replacement.
810 user here and I have a love hate relationship with it. When it works, its very very good, when it crashes / freezes / switches its self off its horrid. Fortunately, and I hope it's not listening, since I did a hard reset and firmware update its been, shh, OK.
When people say they've never had a problem with Garmin units, I believe them, but they generally don't say what usage they put their units to. It seems when using the turn by turn navigation function most problems occur, so if its just being used for recording and display of data then chances of experiencing problems are reduced. My brother has a 1000 and it's fine until he tries to use turn by turn, then it crashes and is unusable.
If I were to lose mine tomorrow, it's replacement would most likely be a Wahoo.