It says it only consumes 25w under full load, and it is a "low profile" card.
Anyone had any luck with a video card w/ the advanced dock? I'm curious what kind of problems have come up
I don't think what you are trying to do is possible. The advanced dock does NOT have a PCI-Express slot for adding a video card (it would be nice if it did). With very few exceptions you are stuck with the card that is built into the laptop (Intel GMA4500 and ATI 3470 in this case). The dock has video out, but it uses the laptops internal card.
If you want high performance graphics you should just build yourself a cheap desktop workstation to use in addition to your Thinkpad. Best price performance combo right now is an inexpensive AMD Athlon X2 (almost any will work) and a good graphics card (ATI 4650 or 4670).
If your only concern is driving more than two displays you should look at a device like the Triple Head 2Go. Although I have doubts about the quality because it tries to drive 3 displays from a single VGA port.