Question on PS3 data transfer

Transfering data from a fat to a slim. I heard that "saved game data" can be transferred over but you can't save over it?? Just wondering if this is true if anyone has had complications from this. Any info would be awesome. Thanks.

Btw...i feel kinda spoiled with 2 PS3's.

I want to know this as well as I am buying a new 250 gig slim to go with my 60 gig launch model and want to transfer all data to the slim. Because I believe my 60 gig is developing a video problem.

well so far everything works perfect. Two games work fine so far.