He's a better WR/KR then he is a CB...much like Devin Hester. He allowed 6 TD's on 60 targets towards his man just this past year alone in college, with a 45% completion rate on passes 10+ yards down the field against him. Neither of those #'s are good at all... And that's not even discussing his tackling ability. Incredible athlete, but we'll see if he sticks as a CB at the next level.
Yes, he needs improvement on those numbers, but I think it's correctable. He did give up a lot of TDs, but he also picked off just as many. This tells me that he gambles and may be a little too aggressive at times playing the ball, i.e. going for the pick or biting too hard on a pump fake. With that said, he is smooth with his back pedal and turns his hips well to go along with that blazing speed. These are traits that's VERY transferable to the next level. He's also been known to bait the QB so he can break on the ball. This may or may not get him into trouble at the next level, but I think that's just the type of player he is, a gambler. He's pretty good at it so I don't think you can penalize him for wanting to make a play though.
The thing I think he really excels at is the deep 50/50 ball. He attacks the ball at the high point as if he were the receiver. He's also a guy who know what to do with the ball in his hands after a pick and the potential for six is always there.
As for his tackling, I agree it's not great. I don't think he'll ever be a great tackler, but I can live with that if his coverage skills reaches its potential. I do think he may be able to improve on it though as he adds more weight. As RS12 mentioned, he's an Olympic level athlete, meaning he was on the track team and most likely had to keep his weight down because of it. With an additional 10 to 15lbs., he may be a bit more stout at the point of attack....
One of the combine weigh-ins that will be very important is USC cornerback Adoree' Jackson. Sources say that Jackson was weighing in the 170s at times for the Trojans, but part of that very low weight was because Jackson is also a track competitor. In the NFL, he will have to gain weight, but in contacts at multiple teams really love Jackson's ability to run the route and prevent separation. Sources have compared him to successful undersized corners in Jason Verrett and Janoris Jenkins.