People give Microsoft Outlook a lot of crap, but if you’re willing to think outside the box, you’ll realize they did all the little things that make life easy. For instance, I rarely use the calendar popup for creating new appointments. No, if I have a meeting next Wednesday, I type “next wed” and hit tab. It’s at 1pm, well, type 1 and hit tab.
Done.

so does Google Calendar.
and you can get to it from anywhere.
I can get to my calendar everywhere on Windows Live. AND I get the significantly better user experience of a client application.
Web is nice if that’s my only option, but I’ll always take a client over a web app.