Just wanted to post real quick to thank everyone for this thread. Without it, I would have been stuck upgrading my card from a GT240 to a GTX750, which initially just left the progress bar hanging halfway and left the machine unbootable.
If you happen to be upgrading from an older card on Yosemite, here's what I did.
1) Keep your original card, update to 10.10.2, reboot
2) Log back in, install the alternate nVidia web driver, don't reboot yet
3) Chameleon user, so edit org.chameleon.boot.plist, remove npci=x02000, GraphicsEnabler=Yes and add nvda_drv=1
4) Shut down machine and swap the graphics card out, power machine up
5) Log in, card should be picked up but may not display the correct res options. If that happens, check nVidia desktop manager for an update and let it update and reboot one more time.
6) You should have all resolutions available.
This was done on an Asus P5Q Pro board (Yep, old school, but it does me for what I need!), so I hope it helps anyone else out there.
Thanks again! =)