As always, I think it's great that the Mozilla team is remembering the Mac "five percenters" with every project. While Sunbird is clearly not ready to compete with iCal at the 0.2 stage, I can see its potential, and the interface alone is worth shouting about.
If anything, all of us who use Macs at home but are forced to use PCs at work can get excellent alternatives to MS's crap browser (Firefox ROCKS on a PC), Outlook (Thunderbird's great if you don't have to network your mail folders) and now, with Sunbird, whatever the schedule program is that comes with office. Keep up the magnificent work, Mozillans!
No problems with opening Sunbird here, but as I said, it's just a concept demo right now and shouldn't be expected to run alongside iCal.
Looking forward to 1.0. . . .