I chose to commission Daylite Designs directly because I needed an App icon and I loved her designs and it was obvious that she knew the ins-and-outs of app icon design (rules, sizes, styles, etc).
I gave her some broad guidelines and she came up with something that looks great and met my criteria. She patiently and quickly applied some of my suggestions, even though she probably knew it wouldn't make it better :)
The final delivery was complete (all sizes needed for iOS apps + the vector drawing). I'll definitely be working with Daylite again.