UPDATE: This may mostly be resolved. See below.
If you're a Windows user, take a wait and see approach to Apple's MobileMe service. This thing is horrible. I'll be reviewing it soon enough, but my initial take on this service, after using it via both Mac OS X and Windows Vista, is that it's half-baked. Here are a few thoughts I jotted down in preparation for the review...
MobileMe's various services are so incomplete as to be almost unusable, especially on the PC side. You can access MobileMe via virtually any Windows-based email application, but you can't synchronize contacts or scheduling information with any PC-based applications, not even the ones built into Windows. (On the Mac, you can sync both.) The Calendar service can't import or subscribe to external applications, so if you're thinking about migrating from, say, Outlook or Google Calendar, you'll need to manually recreate your entire calendar. (On the Mac, you can import into iCal and have that sync to MobileMe.) You can only import contacts one at a time using the Web interface, which is the only interface made available to Windows users. There's no way to seamlessly integrate with any photo applications on Windows, as you can on the Mac, making photo uploading a ponderous and time-consuming affair. The list of problems goes on and on and on.
I can't imagine why any Windows user would ever sign up for this car crash. It's a complete disaster.
Now, I'm hoping and guessing that these and other obvious issues will be addressed over time either by Apple or by enterprising third parties. But why the heck can't you sync between MobileMe and, say, Windows Contacts and Windows Calendar on Vista, in the way that you can with Address Book and iCal, respectively, on the Mac? It doesn't make sense for Apple to continue treating Windows users as second class citizens. Heck, you can't even import/export between these applications and MobileMe in any meaningful way. It's a shame.
I'll keep plugging away with this, of course. But I'm curious if anyone else sees ways around these limitations. Right now, this service just seems terrible to me, and that's before you even get to the more obvious performance and uptime issues.
UPDATE
Someone on Twitter mentioned a MobileMe Control Panel applet. It's installed with iTunes 7.7, go figure, and I never even knew it existed. (Why would I?) Sure enough, you can logon through this thing and sync contacts, calendars, and bookmarks between various Windows-based apps and the service. OK, it's not perfect (there's no Windows Calendar support, naturally, and you can't control which directions thing sync), but this does pretty much solve the biggest problems I was wondering about.
More later. Gotta play with this. :)