1. Yes, all your Google Contacts and Calendar events automatically sync to your phone. Then, if you give the phone your FB login it will match up the contacts with your FB friends and download their profile pic and birthday and updates.
2. As far as the above answer goes, yes.
3. Yes, apps run in the background.
4. Some apps have an option to manually close them in their menu, most others close when you press the 'back' key to return to the home screen.
5. Yes, if you have a plan that allows MMS
6. Google update Android, HTC update Sense. Android versions 1.6 and then 2.0 are due out - possibly both this year. I wouldn't be too surprised if HTC release one more update for Sense this year.
7. Speed is awesome with the v2.x update from HTC. I can understand all the reviews saying the Hero is sluggish as they are all based on v1.x. The camera is a little better now as it has touch focus, but it is still slow and not very good quality (nowhere near as good as the one my previous phone - Nokia 5800)
8. On the SD card you get with the Hero is the HTC Sync application (or you can download the latest version from HTC). This apparently allows you to tether. You can also download tethering apps from the Market, which work on rooted phones.
9. I don't have a Mac - I transfer all my files directly over USB to the phone from Windows no problem though. But I don't have anything that syncs music automatically.
Dave