Couple of things I don't like about the Tavor, at least as a combat rifle, both after seeing the History Channel bit and looking it up on the web:
1) No back up iron sights.
2) It uses a similar 7-lug bolt setup to the M-16. I really, really hate cleaning the star chamber. Not sure how much a gas piston action will help keeping crud out, but that feature is a pain to clean thoroughly.
3) It's still a poodle shooter. Although, the IDF has extensive counter-terrotist/guerilla experience, and don't seem to see the need for anything else.