The 280X should be the best card you can get with native driver support. It's device ID is same as the D700, so, IMO, it's extremely safe for future OSX upgrade.
It's good for OpenCL or video editing. And it's gaming performance is on par with the 680. Also, you can flash it by yourself easily + safely if you want the boot screen. However, the biggest down side is almost all 280X come with at least one 8pin connector, and this card do actually draw lots of power from this port. If you don't know how to power this card properly but just use a 6->8pin cable. Under extreme scenario, it may overload the 6pin power supply, activate the self shutdown protection, or even cause permanent damage.
You better know all the risk and how to deal with them before actually buy this card. And again, this card may suffer from performance issue on the 3,1 (4,1 and 5,1 are fine), so I didn't recommend it at the beginning.
A quick summary, for the 9xx (or the 750Ti), you need to fix the drivers. Otherwise, all you get is a black screen. And you need to fix the driver on EVERY OSX upgrade (or even after a small security update) until Apple provide native driver for the Maxwell card. Although it could be easily done with remote control, but you better know this issue before you jump in. For 280X, you may need to fix the power supply. The best card that I know can work OOTB and no protential performance issue on both 3,1 and 4,1 is the 680. I never own this card, but this is what I know so far.