With the recent rumored casting of Arnold "the Mummy" Vosloo as Zartan and Dennis Quaid as General Hawk, I can say there's now at least two things I think casting has nailed. As a potential third, I'll throw out the no-name guy rumored to be cast as Destro, too. (It's not the Cowardly Lion. That would have brought things UP a notch.)
I'm neutral on Ray "Darth Maul" Park as Snake Eyes as well as the guys who will play Breaker and Heavy Duty. But those last two are gimmes that don't make or break the casting. They could have cast Peter Dinklage as Heavy Duty and it wouldn't have shattered the story of GI Joe (in fact, it would have made not only a great bit of ironic casting for that role, but added some addtional interest on my behalf!)
But the rest of the abominable vomitfest of casting and the fact that the GI Joe mythology has been completely jettisoned to make it a EUROPEAN-based force seems like an overt signal that this production is turning out to be "GI Joe-in-name-only". Channing Tatum is way too young and too much of a "pretty boy" to be Duke (reported here) and Marlon Wayans just shouldn't be here at all. (I saw a clip of Dungeons & Dragons.) At this rate, the film is sounding worse than the name of the new forthcoming Bond flick.
Although I generally like Joseph Gordon-Levitt's work, if Stephen Sommers casts him as a lead villain, I won't be surprised. Hopefully he'll end up as another Joe, but at this point, does it really even matter?