I think Conan is a good move for TBS - even though the show may get a fraction of the ratings garnered by Jay Leno and David Letterman - it's still a step up for TBS. And I think the show is far superior than Conan's Tonight Show - he's relaxed, and no longer trying too hard...no more Conando, Twitter Tracker, or other stupid Tonight skits.
Personally, I generally DVR Conan, and at least check it out, as opposed to Leno, who I never liked, and Letterman, who grew stale for me about a decade ago,
Keep in mind that the big winner in this is ABCs Nightline and local reruns, which now attract all the viewers turned off by the many 11:00 and 11:30 talk shows.