What kills me is that everyone was psyched at the prospect of Marvel characters interacting with one another from film to film, especially The Avengers, and now that it's happening, everyone wants to complain.
I could understand if Cheadle replacing Howard had been bad, but honestly, I didin't miss Howard a bit. I thought the chemistry between Cheadle and Downey Jr. was just as good, if not a little bit better, and let's be series, Howard's voice as War Machine wouldn't have been nearly as authoritative as Cheadle. When he came into the party wearing the Mark II and told everyone to get out, I thought to myself "Yeah. He'll do just fine!"
I'd be more upset at the replacing of Norton if Marvel were doing another stand-alone Hulk film. But even if Norton and Marvel were still on good terms, and Norton were in the Avengers, prospects for another Hulk movie still aren't that great. The Incredible Hulk, despite being a step-up from Ang Lee's version, didn't fare much better financially, so it's not really in their best interests financially. They can lump him into an Avengers film and it's fine, 'cause the primary characters are going to be Iron Man, Thor and Captain America. Yeah, those two separate films for Thor and Cap still need to succeed first, But they've got some good points in their favor. A solid cast (Anthony Hopkins as Odin is just a master stroke), and a proven director whose love of Shakespearean drama and gravitas can only be a plus for a character like Thor. And while many folks will scoff at Joe Johnston over The Wolfman, he's still got a few solid films under his belt, not to mention a comic adaptation that still holds up today, and exhibits the perfect tone and time period for Captain America. And again, you've got a very strong cast for the film. Hugo Weaving as The Red Skull? When has Weaving failed at villainy? If just doing the voice for Megatron, say what you will about the Transformers films in general, you can't tell me his voice work wasn't great.
Favreau leaving Iron Man, I don't see it as the end of the world. For every example someone will point out of a comic book sequel failing from a change in director, there are just as many where director changes didn't prove to be detrimental at all. Why Favreau left, who knows. We can speculate and scrutinize everyone word from every article and interview we read, but none of us can say for sure.
It just seems like some of us are just being really quick to take every change that comes about as a bad omen.