Tannehill has incredible accuracy at times... I've seen him make throws that no more than 5 other QBs in the entire league can make.. he also has adequate arm strength (not superb but not weak). He also has great speed and elusiveness as a runner but does not use his legs like he should.
He needs to work on pocket awareness obviously... the clock in his head, ability to step up in the pocket, slide around to gain that extra half a second... he needs to learn to throw the ball away rather than take a sack. He needs to learn when to take off and run.
In my opinion the positives outweigh the negatives with him.. I think that with more development, as well as him working on his flaws, he could turn into a top 4-7 NFL QB.. good enough to get us deep into the playoffs. Not to mention our run blocking and pass blocking have both been atrocious.. that doesn't exactly help a young quarterback.