I would figure that, if the non OE part is a quality part, then you should have no problems. There are two states for the T-Stat: Open, closed. I can't really see how one can be 'better' engineered than another (this does not include the material from which the part is made of).
I checked out the AA t-stat, and I'm thinking I might not want to go with that cool of one.
Matthew, that's good info., I didn't realize there were 3-stage t-stats.
I think at this point, I'll order the Bavarian Auto t-stat, and some Water Wetter, which is supposed to drop the coolant temp by a few degrees. While I'm at it I'm thinking an aluminum housing might be in order! I'm getting ready to change out the radiator fan anyway, so might as well do it all at once.