On the competence side, the fact that Obama has not seen fit to push Lieberman over the cliff may be seen as useful, in the following sense.  All observers agree that Lieberman appears to have been incompetent or at least negligent in his oversight of Homeland Security.  But that might be fine with an administration that needs to fix the problems.  Not having investigations while cleaning house may be useful.   It depends, or course, on whether an investigation will help in cleaning house or not.  Obama may well including the calculation that Lieberman's negligence/incompetence provides less oversight and more room for internal reviews without the peskiness of an oversight committee.

On the political side, now Lieberman owes Obama.  Big time.  It will be interesting to see what he will be expected to pay.