I have bought a few deals from Groupon and am quite satisfied.Most of he deals are quite average but sometimes one finds a good deal and something that one desires. Like the time I bought a Sheaffer pen or the Gold Plated playing cards.
Most of the deals are quite pedestrian and can be had straight from the shop also especially restaurants, spa etc, if you quote the groupon deal there. But that is part of the charm of the website, just because it has a deal, the footfalls in the outlet increase with real customers.
As far as things like watches are concerned, it is always a case of Caveat Emptor. Look discerningly and you will get what you want. Just be on the lookout.