Airset: great syncronization with your desktop and Palm setup. I like the one-stop-shopping theory behind Airset. A little slow. Printouts could be better.
GCalendar: a Google product so confidence from the start. Inputting items is lightning fast. Syncs with Remember the Milk which is nice. Month view could use improvement.
30Boxes: super simple and blazingly quick. Nothing more than you need for a calendar item. Has two different view features which is nice.
Which one am I leaning towards? Right now it's a battle between GCalendar and Airset. I'll keep you posted. Speed, aesthetics and syncronization with my Palm Treo are of primary importance. I also wanted to go online after reading this.