Technique- The most over-rated aspect of the game, particularly in India. You don't need seven Rahul Dravid types in the same team. In fact, that can do more harm than good. Looking at some of the top teams in the game, Australia don't have too many 'professors' in their team, and they still get the job done. Pakistan have Afridi alongside Younus and Yousuf. Even technically limited players can be an asset, if used in their best positions. Uthappa may be used best as a rapid-fire opener, rather than one to score centuries and double-centuries regularly.
Batting position- That number seven slot is not meant for specialists. That's one where you either have to smash everything around the park, or just surrender (not a viable option, obviously), and you don't want a specialist batsman there. Uthappa batted as a lower-order hitter, and while he played one good innings, he did nothing of note since then, batting more like Ricardo Powell than a quality frontline batsman. His average suffered, as a result. As an opener, he can afford to play himself in, to get a big score.
Versatilty- Most of the power players of today (almost all of them) have a second skill to fall back on. Gilchrist is the best wicketkeeper in action- or he was, before he retired. Symonds is a more-than-useful stock seamer/spinner. Gayle is a full-time offie who's very effective in the final overs. Afridi is a highly productive leg-spinner. Flintoff is often a frontline pacer, while the seam-up service of Styris and Oram is valuable for the Kiwis. This can go on and on, but in comparison, Uthappa has nothing. If he bats like any of them, he'll have a sub-40 average, which is not good enough for a specialist batsman. If he's short of big scores, he may lose his place to Gambhir or even Jaffer. The big innings is the key.
By far, his best innings was that one in a limited-overs match in Vizag (?) against the West Indies. He looked unstoppable, hitting freely and running hard. The bowlers simply couldn't get him out, and finally, he got out taking one risk too many. He's not one who will throw his wicket away, but one who will try to do near-impossible stunts like hitting two sixes off Brett Lee in an over or running on Ponting's arm.