It's been hinted on twitter that he's somewhat "gamed" the system to use Kentucky as a training grounds for the NBA, and we all know Calipari's history so... even rumors are going to hold more weight. Personally, I say who cares, the college game is as corrupt as any other pro sport.
The way I see it, he followed the rules, he saw an opening that looked useful, UK was OK with it, and he took it. Had he not gone to UK, he still could have been eligible for the draft this year (see Leonard Miller, potentially prep-to-pros this draft) and might have actually had a bit more game tape to go on.
My (current) worry on Sharpe is the paucity of game tape against elite competition, but not the UK situation. If some other character stuff comes out, so be it, but for now it's all about talent and none about character.