I've been running my XPS 1710 with the Nf7900-GO on the D-dock and the smaller dock without ANY issues whatsoever. I changed the MXMII video to a 7950 GTX and still no issues -the dock has a beefier PSU than the standard AC wallwart that comes with the laptops.
you can fit ANY full sized video card with a PCI slot in the dock- there is a metal tab that can be removed with one screw that Dell sort of put in to try and ...discourage customizations, but really, you can put in a giant RAID card in there too, if you want (you're on your own on how to power the HD's, though if you know what you're doing you could easily wire in a few rails and change the voltage a bit... someone ought to make a little customizer for this- to add a D-DOCK NAS device directly INTO the D-Dock- could be done, esp. with the new 500+GB 2.5"'s on the market right now!!!!
ANYTHING will fit in that fits in the PCI slots. (No it's NOT PCIe though!).
If you have a Matrox PCI it will work fine. I tried my old one, (G400 pci, hard to find!) and my old ATI pci rage pro card, no issues. THEY WORK GREAT as long as the cards themselves have the umpf to power the displays. THAT IS THE BIGGEST ISSUE. Unless you can find someting like a ATI 9800pro PCI, though, 3d and CAD work isn't going to be too hot. However, adding two more 19" LCD's for 2d office work, or light 2d cad work, with the BEEFIEST PCI card you can find (it's a NORMAL pic slot, with ROOM for a full length card, like an old voodoo) you can have a ton of options.
Right now I have a Delta 1010 professional soundcard in mine (it has a break-out box rack mount for the real converters) for when I'm doing pro audio.
ANY D-Dock with work with ANY dell laptop that supports the same bottom jack they make, except possibly the newest XPS with the SLI cards- which might need more power than even the D-docks can handle- someone else will have to test that as I don't have one around to try out.
I've tried 10 "different" D-Docks and APR (Advanced Port Replicator) and all work just fine.
From my understanding, you HP users out there are ALSO going to be happy with a similar solution for your HP presario rigs. The HP dock that is similar to the Dell D-Dock also has the same features. I've yet to pick one up, but one is in the mail for my MOM and I'll check out what it can do when I set it up for her in her home office.