I haven't tried it yet, but there's not really a whole lot that I can see being able to go wrong with it. The two people's games don't directly interact with each other. You don't even have to be online at the same time, and there's a 24 hour window to accept/refuse requests. If you ignore them they're automatically cancelled. My guess is that all sim imports/exports are handled through the Sims 3 website, with a system similar to the Exchange...and since that's already a tried and tested system, you're not likely to encounter many bugs in relation to it.
I'm only theorizing, however.