Thanks Vincent.
A couple more things.
One thing I didn't say in the O.P. -
Do you choose to writer long vs. short due to financial considerations? (all surveys/indications/folklore is that novels sell and short stories don't)
just wanted to say that one of the best short stories I've read in the last couple of years was a collaboration by Elizabeth Bear and Sarah Monette called Mongoose. I looks like you can read it on line here if you are interested:
http://books.google.com/books?id=nHA...onette&f=false
I read it in the Year's Best SF #27 as per that link.