This is all my own perspective, of course--whether I'm evaluating myself accurately or not, it's hard to say. ;)
Things I think I do well:
1) Characters--I think I do a pretty solid job of developing characters, giving them nuances and dimensions that made them three-dimensional, and portraying them in shades of gray rather than "good guy" and "bad guy." I have a lot of fun figuring out quirks and backstories even for relatively minor characters.
2) Endings--While they're never perfect the first time out, I find I'm usually able to pull off climaxes that tie the stories threads together and are emotionally satisfying, without being predictable.
3) Premise--I come up with lots of unique ideas, or twists on done-ideas, that seem to stand out from the crowd.
Things I think I need to work on:
1) Dialogue--I think I've gotten better at this, but I still have to really work at making different characters "sound" different and believable.
2) Setting/Description--Something I've struggled with a long time. I've had readers say they really like my descriptions, so obviously I've made progress, but it doesn't come automatically yet. Part of the problem is that, despite being a very visual person, I don't usually visualize stories when I'm reading them, so I don't do it with the stories I write, either, unless I make myself. Which means I have to keep reminding myself to dip into the sensory experiences of the character in the scene.
3) Structure/Big Picture--I've commented before that I have trouble stepping back and looking at a novel as a whole, how all the threads work together and play off each other. So sometimes I neglect elements that should come into play, which can affect plausibility, consistency, pacing, etc. This is why I always outline carefully before writing, and re-outline before a rewrite.