What is the best Shared Calendar implementation for machines running OS X? I would like to set up a shared calendar system for our office of 4 people. Optimally, I would like all (or as many of) the features from Exchange but built in such a way that it all ties together with our Snow Leopard/Lion machines.

What solution should we go with? I think these are our options:


Lion Server: I tried setting this up last month (after launch) and it was a disaster. It was terribly slow on our MacMini server and Wikis just stopped working suddenly, which worried me that other services (such as calendaring) would stop too.
Exchange Server: Lots of overhead and pretty much overkill, as we already have an email solution and wouldn't use the other Exchange stuff. That said, I guess you can get hosted Exchange accounts for $10/mo from RackSpace.
MobileMe: Not really shared calendar because I can't easily see a coworker's schedule.
Google calendar: No.
...?


Apple fans, help me out! What are your suggestions?

If I'm making incorrect assumptions or completely glazing over something please let me know!
For a small office, you may be able to get away with using BusyCal. It works well for sharing calendars with a small workgroup. You can turn your co-workers calendars on or off so you can see them, or not, depending on your need to de-clutter your calendar. It's worked flawlessly for us with MobileMe calendar sharing, or you can set up your own CalDAV server. Free trial, excellent support. I'm a big fan.

You said:


  MobileMe: Not really shared calendar because I can't easily see a coworker's schedule.


I think I need more info, as I have no problems viewing the shared schedules of the other people on our system.