Meh, those dual-GPU cards are just like SLI/X-fire setups in that they're hit-or-miss.
They'll excel in some games, suck in others, and be mediocre in the rest.
Not nearly worth $600.00
if you ask me.
Hell, you can get 2 8800GTS 512s and an 780i SLI motherboard for less than that.*
*Okay, well, almost.