OS X Lion is one broken big cat
Stay far away from OS X Lion if you value your sanity.
If your iCal broke when you upgraded your mobile device(s) to iOS 5 and iCloud, this will not fix it the way you want. Oh, it might start syncing again, but it will drop all of those events which you created in between. They're just GONE.
Likewise, your "to do" tags in Mail.app are also going to disappear. They might show up in iCal, but it's a trap! If you click on one of them in iCal, you get a "open in mail" link. Actually using one of those links leads to an unusable system. Mail comes up and starts grabbing all keyboard input. You can't switch away from it and you can't close any windows.
You finally have to force-quit Mail.app to get your system back. If you're following along at home, this means you can't ever get back to your "to do" items. They, just like the iCal items, are GONE.
Get familiar with the system control panel/preference menus, since you will be using them a lot.
If you use the scroll bar to tell you things about documents you are looking at, you will have to grovel around in there to turn it back on.
Maybe you use three finger swipe gestures in Firefox to do home (up), end (down), back (left) and forward (right). None of those will work out of the box. You can get back and forward to work by twiddling things in system preferences, but you have to add a third-party program to get back the home and end gestures!
Then, if you're used to using three fingers to flip through mails, you will have to go back to that third-party program to override the hack you just made. This is after you revert the majority of the interface changes in Mail.app, of course.
Do you ever use the pinch zoom feature on your desktop? Kiss it goodbye. It's gone.
I'm wondering if I should go to the trouble of wiping this thing and starting over from my last backup. It's that bad.
Have all the tech outfits lost their way? What is going on here?