Hi save2600, 
I recently purchased the Competition Pro USB version for £12 and it works a treat on the Mac and a SNES USB gamepad for £7 from china which also works fine on the MAC, best of all there was no need for adapters or drivers... 
Glad you're able to make use of those things. To me, there's no substitute for a good old fashioned 2600 joystick. Gameplay and feel using one is incomparable IMO

Oh and the Stelladapter allows you to use 2600 rotary paddles too. LOTS of games (even in MAME) benefit from that. No drivers needed either with a Mac btw.