DO NOT UPGRADE TO LION!
Lion may well turn into to Apple's Vista. I've used Apple products since 1981, and I've never experienced anything like this. The so-called upgrade has so far:
1. Broken Mail and all it's contents. No obvious solution that doesn't result in losing all folders.
2. Time Capsule, by virtue of a complete new backup of the HD, eliminates most history as there typically isn't sufficient memory for the doubling up. NO WARNINGS. Just gone.
3. Applications that don't play nice with Lion (PPC apps, Adobe apps, Microsoft apps) are just eliminated when a TC restore is done following the upgrade.
4. Apparently going back to Snow Leopard is problematic, if even possible.
I hate that I didn't wait. What an idiot.