As a shop owner and teacher, I appreciate patterns that are not just visually pleasing, but are well written and include multiple sizes. I've found some adorable patterns, but in order to teach them or kit them, I've pretty much had to re-write the instructions in order for the average person to understand them. Too much work!
Two designers that meet my above criteria are Eleanor Burns (Quilt in a Day) and Terry Atkinson (Atkinson Designs). Of course there are many other good ones out there but those are the first two that came to mind.