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I played around with DP4 and it does work and works quite well and fast and smooth. I have ordered so more RAM to move it up from 2GB to 4GB, which I've been meaning to do for some time now. The RAM will be here tomorrow and I will be ready for Lion!
 
Running it on my BlackBook. Also runs well, quite smooth. No multi-touch gestures, of course, but still useful. I have launchpad set to CTRL+SPACE, mission control to CTRL+UP, and I can switch desktops with the standard CTRL+left/right keys, so navigating is fast enough for me to not be bothered by the lack of MT gestures.

OOTH, AirDrop is not supported (and Apple doesn't make it clear anywhere other than to just not show it).
 
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