Is Thunderbolt backwards-compatible with mini-DP for both input and output? How compatible or not is the new Thunderbolt connection?

If I have a MacBook Air with Thunderbolt, can I use my existing mini-video cable to connect it to a VGA overhead projector?

If I buy a new Cinema Display with Thunderbolt, can I connect my existing Mac Pro to it?

Are there special cables, convertors needed, or are there any fundamental incompatibilities?
Your existing Mini DisplayPort cable (VGA adaptor, etc.) should allow your Thunderbolt equipped MacBook Air to connect to a projector (assuming it worked previously with a Mini DisplayPort output) but, as with all things presentation, you'll want to test the setup in advance if possible.

According to Apple's specs, the  Thunderbolt Display requires a:


  Thunderbolt-enabled Mac computer, including MacBook Air, MacBook Pro, Mac mini, and iMac


Your existing Mac Pro can't use the monitor.