I'm confused about what actual model number this is. After selecting "4-port for Mac Pro" the picture on Amazon shows a card with no power connectors and the model "ktu3fr-4pa" silkscreened on it. This is a model already recommended in the front post and people who have bought it have hooked up power. Looking up that model number on Inateck's website verifies it is "for Mac" but also shows it has a power connector and power cabling.
http://www.inateck.com/inateck-ktu3fr-4pa-4-port-usb-3-0-pci-e-express-card/
So definitely please report in with what you get and what the model number is. Perhaps newer revs of the board don't require supplemental power and older revs do? And they haven't updated their website? Very confusing.
I don't know. In the last month or so 2-3 people have reported problems including locking up for large transfers and constantly ejecting drives.
I'll update the first post with the latest reports and a "YMMV" warning.
Mine still works well. I do get an eject warning after waking from sleep, but the drives remount themselves. Sustained transfers work fine. FWIW, I'm still on ML.