I recently commissioned a costume from CosplayMandy, also known as cosplaycommish.
I was actually a little reassured by the 'half now, half when your costume is done' deal she has going on, since I'm only investing a portion of the money until I see what I got. And what i got was AMAZING. Her sewing really stands up, the costume feels sturdy and flexible, the colors and styling were all spot on, and everything was very easy to get in and out of thanks to the well-hidden zippers in the costume.
She's a little quiet during the process, but that's completely understandable. I'd rather a person be working on my costume than giving me updates on it every five minutes, and I felt like if I'd ever wanted a progress report, I could have emailed her for one. Right about the time I felt like asking anything, she was ready to ship the completed costume out! Right on time. She was also very friendly throughout.
I'm definitely looking forward to commissioning from her again...and of course wearing the costume at this years Dragon*Con!