And Sarah, I find that I have to write for one person at a time--if I'm doing two people at once, it takes me awhile (especially if the two are having a conversation) because I have to 'pretend' their personalities to figure out how they will respond to something. For some characters, it doesn't take long at all--I have such a good handle on their personality and know how they will react to a particular stimulus--on others, I really have to think. And a lot of my stuff seems stilted to me, mainly because my father drilled proper English speech into me, and I saw first-hand how speech affects reactions and first-impressions, so I worked hard to sound well-spoken--playing characters who don't speak well or properly is particularly difficult for me.
You should see me play a character--when I really get into it, my facial expressions and gestures will be those of my character (not necessarily me)!
At one time, I thought about getting a job as a proof-reader/editor for a publishing company or something of the sort--I do really well unless I've written the work I'm proof-reading.