Personally:
1. Barragan, for reasons stated thusfar. Even though I think Starrk can beat him.
2. Ulquiorra. Even his first release was not just above Vizard Ichigo, but so far above him that nothing Ichigo did could so much as put a scratch on him. Even with just his first release, he'd be third at least. With his second, he's a shoe-in for #2.
3. Starrk. His guns are very abusable, and he shows good skill, speed, and strength. I think it was pretty strange how he never seemed to be able to hit anyone with his guns when he should have easily been able to.
4. Yammy. We'll see more of him, but his current size and apparent ability to heal when he gets angrier should at the least put him this high.
5. Grimmjow. I'm pretty baffled how Nnoitra is supposed to be above him. His Hiero didn't seem that much stronger, and Grimmjow certainly is faster and has much more varied abilities.
6. Szayel. His Gabriel ability pretty much gives him auto win if not specifically countered in a way like Mayuri did.
7. Aaronario: If his release really has the powers of thousands of hollows he should be first on the list, but he really didn't demonstrate this at all.
8. Harribel: She just didn't seem effective and losing one on one to Hitsugaya was just lame as all hell. Her released abilities were clearly running on the low end of creativity.
9. Nnoitra. He's a brawler, plain and simple. And not very effective at once, doing worse than Shikai Ichigo against the same opponent is just pathetic.
10. Zommari. Do I really need to say anything? He was just sad and pathetic. I'd even put pre-released Yammy above him. He could have won if he just took control of Byakuya's brain right away, but apparently he's too stupid to think of these things. With that power, he could have been one of the best.
As an honorable mention: Luppi. I'd probably put him between Harribel and Nnoitra.