The difficulty with most of these sites is not that they are criticizing Orthodox Christianity as it is but basing their critiques on misconceptions of Orthodox doctrine and practice. Sometimes elements of Orthodox teaching can be recognized, but the way they are put together is often quite bizarre. Irenaeus of Lyons wrote about how heretics took elements of the faith and rearranged them, so that what once was a mosaic of a king becomes an image of a dog (or something else).
The exception to this is Daniel Clendenin, who obviously has done his research. He has a much better understanding of Orthodoxy than the other writers linked here. His basic conclusion though is that "I'm not Orthodox because I hold to Protestant Reformation Distinctives" -- at least that's honest.
- "Why I'm not Orthodox" by Daniel Clendenin. Christianity Today
Roman Catholic Polemics
- Orthodoxy and Catholicism: A Comparison - Dave Armstrong