Even though we don't get our own products Wi-Fi certified, my lab does make sure ALL of the gear we test our devices with, are themselves WFA certified. That includes AP's, client cards, and USB dongles.
A year and a half ago, I made up a pretty comprehensive list of the non-"n" dongles out there in the market place. In addition to price, it listed power and sensitivity claims, chipset, source, WFA certification #, review highlights, and any caveats I came across - like a tendency to run hot, etc.
For information sources I used product catalogs, specifications, customer reviews, manufacturer websites, and of course the WFA website. Virtually anything I could find. The final list contained dozens of dongles, and it took quite a bit of time to cross check, verify, and finalize.
It was a great list, appreciated by everyone who used it. Unfortunately, less than a year later it was almost useless. And now, with all the 'n' devices out there, about the only thing it's useful for is historical reference - and maybe a blotter.
New devices come out so fast, it would be a full time job just keeping that one list updated.
I really wish I had a up-to-date comparison list for just WFA certified 'n' dongles, and although it would be interesting to write one, who has the time?