People shouldn't try to mess with Clarke as a cricketer based on his T20 performance. The fact is, when India play Australia in Real Cricket (TM), Clarke is definitely one of the players that could do massive damage with his ability to play spin.
Yes, he may not a be a real good T20 batsman, but he is an excellent cricketer. I'd love to have him in the Indian side any day. It's not too far fetched to call him the best batsman in the Australian Test team as that article posted by Sir Alex suggested. He's an excellent player, and will probably remain the backbone for a while now that Ponting (maybe) is winding down.
IMO for the sake of his confidence, he should focus on the format he excels in (obviously personally he'd want to prove his mettle in all formats, but the selectors should think of Test cricket and rule him out). I don't know how good or bad he is in ODIs, and don't much care, but I know he's a great player in Tests and his shortcomings in this format may mentally start to affect him in the longer format, and that would be a shame for Australia. Though obviously I'd love for him to be short of confidence when he comes over to India for that Test series, especially as now Hayden is out of the picture and he could potentially be that "dominating-spin" presence in the lineup.