Sadly, even with using the OS X driver for Xbox 360 controllers, it refused to work with my OS. I could get it to work with Microsoft's driver on Windows 7, but I don't use Windows and I wanted it working with sdlmame on OS X!
A email was sent to the author of said driver with no response for over a month. So after I got bored of waiting, I went on a search. I found a post on Shoryuken.com for some Hori stick (and found some other posts along the way) but this one gave me enough information to make my own "driver" and that was good enough for me!
Open up my good buddy the terminal cd to "/System/Library/Extensions/360Controller.kext/Contents/" and use your fav editor of choice to edit "Info.plist" (mine being pico for terminal editing), look over the file, it should be obvious where to insert this next bit of information... (copy n paste it, this blog is cutting out some of the text from displaying, but if you copy it, you'll get it all)
<key>SFIVFightStickTE</key>
<dict>
<key>CFBundleIdentifier</key>
<string>com.mice.driver.Xbox360Controller</string>
<key>IOCFPlugInTypes</key>
<dict>
<key>F4545CE5-BF5B-11D4-A54F-000A27052861</key>
<string>360Controller.kext/Contents/PlugIns/Feedback360.plugin</string>
</dict>
<key>IOClass</key>
<string>Xbox360ControllerClass</string>
<key>IOKitDebug</key>
<integer>65535</integer>
<key>xfvbfIOProviderClass</key>
<string>IOUSBDevice</string>
<key>idProduct</key>
<integer>61496</integer>
<key>idVendor</key>
<integer>7085</integer>
</dict>
I named it "SFIVFightStickTE" because hardware wise, it's the same thing. But it has a different key needed to get it working correctly. Add that to the file, save it, open Disk Utility and repair permissions on your drive, and reboot.
Plug in your FightStick, setup MAME, and enjoy. I know I am!