As a completely unbiased opinion (basically...I don't give a crap), I think some are being a bit hard on Avatar. When this was announced, absolutely NOTHING had even started. And while Avatar is not my favorite franchise by any stretch, a good ride is a good ride. Avatar has the potential to be translated into a great theme park area, it all depends how far Disney is willing to go with it.
I definitely agree with the fact that a good ride is a good ride. I could really care less what its themed to.
The problem is, is that Disney isn't willing to go very far with this. When was the last time Disney created a "good ride?" I guess Everest could be argued, but it's kind of gone to crap now. The likeliness of TDO giving this what it needs is unlikely. Plus add a mediocre franchise to the mix and it creates a sour taste in most people's mouths.