Thought I'd look at MC22 on Snow Leopard for interest for the community as I have an old macbook still running. I have not used it for MC until today.
Good news is that MC 22 runs very well on my machine for 2 channel audio. I installed 22.0.30 and restored a library from my everyday machine. A wide range of several thousand lo-res, hi-res and dsd tracks were displayed and played as normal, the files being streamed from a NAS. Output was to internal speakers (!), a USB dragonfly or via usb to another external DAC. I have not pushed any limits here but it seemed to be running as well as with more modern machines and OSXs.
Better news is that it also runs 22.0.41 (latest version as of now) in audio mode in the same way. The only aspect that does not run is the new Theatre View facility but if you call this up with CMD-4, its not fatal. The screen goes white but normal service can be resumed by dialling in CMD-1,2 or 3. Resilience or what!
I have no video loaded so cannot comment on the video playback capability.
The Macbook runs on 10.6.8, is powered by a 2GHz Intel core 2 processor with 2GB RAM and a 128GB ssd. I fitted the ssd and this may help keep it moving along. It gives a benchmark score of 1187 JRmark.
I hope this gives others with only Snow Leopard devices the incentive to have a go, at least on audio!
Mike BRG