All of the new rev3.0 and slims that go out in about a week or so will ship with the new bracket. The slim design has been changed to accomadate ATI X2 card better. There is NO WAY I will change the 3.0 design for these 3870X2 cards, cuz the unit is perfect and the card is most definitely not ;).
On the old slim/3.0 bracket (2900,8800u), the fit is great with those cards but with GTS it's a little off, as that card was released after current bracket was done. New bracket fits All the old cards still + GTS + 38070X2 + 9800GTX which launches in about a month :D.
New 4.0 unit for NVIDIA'S new flagship card is specially designed and tested specifically for that card... it has to be that way for this unit to be the best it can be with that graphics card. Slim unit will be geared more towards TRI-SLI and ATI X2.

