The best way to describe this game is "good, but flawed." The companion characters are generally likeable, but are also fairly one-note in their characterization. The various factions are all interestingly developed, but it's pretty dang clear that the kill-for-science and kill-for-religion groups absolutely suck. The combat is fun, but repetitive fights and easy-to-cheese enemies get obnoxious after a while.
If I was to sum this up in a single sentence, I'd say: "What is Bioware wrote James Cameron's Avatar?"