In my view, OF does "do priorities", just differently and better. Just like Photoshop doesn't sync its layers with MacPaint, Daylite doesn't sync its relationship info with AddressBook, Acrobat Professional doesn't sync its form layouts with Preview, etc.; I think that it's worth trying to do it the OF way instead of trying to get OF shoehorned into iCal. Said another way, I think that OmniGroup is well aware of this request.