I just got a Yamaha N12 to use with Apple Logic Pro 8. It is now working, but the initial experience was not good. I thought I'd share what fixed it.
Initially, Logic Pro was happy to use the N12 for audio in/out, but the control buttons (Play/Stop/Record) on N12 didn't work and neither did the MIDI interface. Worse, my existing MIDI interface stopped working.
I found that there is a major upgrade to the N12 internal software ("firmware") and the Mac client software. Installing this fixed all the issues. I can now Play/Stop/Record on Logic Pro using the buttons on N12; the other DAW Remote Control buttons don't do anything useful, but this is expected, according to documentation. MIDI works great, now, too, so I can sell the old interface.
You need "Tools for n V2.0.0" first, then the IEEE1394 Firmware Updater, then the n8/12 Firmware Updater, then the Sweet Spot Data Updater, in that order. Each comes with detailed documentation, so while it takes a while to do, and is a bit nerve-racking, it's not actually difficult.