Newbeing hit the nail on the head. I agree with his points. At first, I was concerned about the immersion, but after seeing it in person, I am glad that Gearbox has done it in 3rd person. As he points out - there are so many things you can do with the camera in 3rd person that just wouldn't be as effective in 1st person.
Probably the biggest sticking point is the aid to teamwork that Newbs mentioned. I think that really helps the xeno players plan out attacks and encourages a team work approach.
I feel like it's a great counterpoint to the marines being able to use the motion tracker. the two act to balance one another from a gameplay perspective.
All I'd say is wait to reserve judgement until you get a chance to see it in action. It's not going to be everyone's cup of tea, but I think it will appeal to a very wide range of players.