You never sat through the Lord of the Rings movies, the Pirates of the Carribean movies, The Dark Knight, Benjamin Button, Watchmen, etc. and won't sit through Avatar or most other big special effects movies in the coming years?
Mo-cap has its place; generally for nonhuman/mutated/otherworldly characters in live-action films. We already know there's classic 2D animation in this movie, so at least its not pure mo-cap, and if Zemmickis isn't totally mad there should be live actors as well.
Basically I'm staying optimistic until I start hearing actual plot/casting/promotional details.