Yes the PS3 can auto restart where you stopped on DVD's and most BD's. The only exception is where the BD's are 2.0 Live. And the ability to do restart where the BD was stopped came with one of the more recent updates.
I own two PS3's, one for 19 months and one for 7 months. There have been many firmware updates for it. This, the BD software forum and PS gaming forum are all loaded with knowledge about what the PS3 can and cannot do. I suggest any owners who do not go to those forums to do so as it will greatly increase your appreciation for what the PS3 can do. As of yet it is still considered one of the best, if not the best BD players available for all it can do.
One more update that gamers are waiting for which is in game chat and it will be considered a "perfect" media machine by many.