I get password strength under the password box - it goes from "Insecure" (red line, red text) to "Very secure" (green line & text).
Event photos come up in one long column, rather than in rows... and I can't see the karma value - just the karma bar... Otherwise I think it's pretty much fully functional from a Mac - everything seems to work OK anyway
There are small differences - e.g. when you hover over someone who's attending an event? On a Windows PC, it shows their BM ID... on a Mac, you have to click through to their profile to get it... but I tend to click anyway cos I'm a nosey moo