Cool! I was looking at upgrading to the Thunderbolt, but I was going to possibly wait until after our trip to Disney in June just because of the Mobile Magic App.
We used it for our last trip in June 2010 and I found that it came in handy quite a few times. The app is actually connected with Disney's network so that it shows the exact "Stand-By Wait Time" and "Fastpass Return Times" for various rides in the park.
It especially came in handy when we were in the middle of the park and wanted to decide which Fastpass to send a runner for next (We were a party of 18 on that trip). By accessing the actual return time of the Fastpasses being distributed at that moment, we could make a more informed decision without running around the park.
Speed