I haven't checked the forums, but at http://www.rme-audio.com/english/firewire/ff800.htm, it shows driver support as follows:
Driver support
Windows 2000 SP4, Windows XP/XP64: Full ASIO multi-client operation of WDM, MME (not XP64), GSIF 2.0 and ASIO 2.0. WDM (DirectSound) with stereo and multi-channel support. Full hot-plugging. Up to 3 units operational.
Mac OS X (10.3. or up) and x86: Core Audio, Core MIDI. Since 10.4 (Tiger) up to 3 units operational.
It doesn't show ASIO drivers for mac. The TotalMix page at http://www.rme-audio.com/english/techinfo/hdsp_tmhard.htm doesn't say one way or the other, but all the pix definitely look PC-like. In general, though, all these pages look pretty old, and have old copyrights showing. That's why I asked. I'll take a look at the RME forum.