Hmm. So I'm the one lonely person who bought their SE version from Circuit City?
The mobile content they offered was useless to me - since I'm one of the roughly three people in the US who doesn't own a cell phone - so I can't comment on that.
But the extra footage was neat. It was basically four more behind-the-scenes segments, in Flash video format (good quality, though):
1. Voices - Commentary about the logistics of the voice acting, as well snippets from their recording sessions. It was neat seeing the characters' voices coming out of, well, the normal-looking guys. My favorite out of all the segments.
2. Metal In Motion - Preliminary effects. Various early animation sequences and model tests.
3. Stunts - Info about the logistics behind the various action sequences.
4. Gearing Up - Guns. Lots and lots of guns.
Considering that a transforming case would just be one more knick-knack, the Walmart one wasn't the SE version, and I knew I couldn't get out to the stores in time to snag any of the limited goodies on release day, I think the CC extras were worth the choice in store for me.
I love behind-the-scenes stuff.