I've been running Mac BIAB 2009.5 and (as of yesterday when it arrived) Mac BIAB 2010 on a two or three-year-old MacBook Pro 2.16 Core Duo with system 10.6.3 and 2GB RAM (I'd upgrade the RAM, but 2GB is max for this model). No problems with pops or clicks with BIAB when playing styles based on RealTracks. I do find that if I select the Apple DLS synth instead of the Core Midi driver, and play a style that uses both RealTracks and midi, playback of the midi tracks can stutter a bit with occasional pop or clicks -- seems like the processer doesn't like to deal with DLS and RealTracks at the same time. I haven't noticed this when relying on an external midi synth playing back via Core MIDI. And I didn't notice it when using Bandstand and Core Midi along with RealTracks -- though I've stopped using Bandstand because of compatibility issues with Snow Leopard.

As an aside: I also noticed a lot of popping -- much worse than the RealTracks/DLS synth issue -- when using Windows BIAB 2009 on this same Mac, running the Win version via Parallels. Numerous inquiries to Parallels' tech support failed to resolve the issue, so I switched to VM Fusion, imported the same virtual machine from Parallels into Fusion, and the popping problem went away. Now that I have the latest Mac version of BIAB, I probably won't be using the Windows one much. It's just a lot easier to run the Mac version on a Mac (despite the lack of a decent, Mac-compatible GM software synth, for which I can't blame PG. But it does leave me either putting up with stuttering and tinny DLS sounds; GarageBand/Logic sounds that don't cover all the GM bases; or toting around a Ketron SD2 along with my laptop... all things I can live with, given all the other advantages of the new Mac version of BIAB, including the DAW plug-in.)