I was asked this recently (on an application form) and found it hard but interesting to answer. The external stuff is easy enough - I have a ferocious work ethic, I take criticism well, but I could procrastinate for Ireland at times! - but what about inside the work?
I'm poor at dialogue, and have a bad tendency to 'write up to' big plot events - I need to remind myself constantly about 'getting in late and out early', otherwise I would narrate the heroine meeting her future lover from the moment she woke up that morning and dampen down the drama of their encounter by following her to the supermarket afterwards!
Harder to say what I'm good at. I think I'm good at place and atmosphere, and I've got a lot better at characterisation-in-action and showing a character through action, rather than telling the reader what he is like.
Anyone else?