I was checking out the SDSS fields that didn't solve. I grabbed the original SDSS images and ran them through the web version - for 1 out of the 3 fields, I got an instant solve!

It looks like Simplexy is doing a better job of finding the brightest objects. Way to go, Blanton!

Original image: http://cas.sdss.org/dr6/en/get/frameByRCFZ.asp?R=5390&C=5&F=191&Z=0&submit1=Get+Image

Image + SDSS pipeline source extraction: http://trac.astrometry.net/attachment/wiki/SimpleXyVsSdss/sdss%2Bf1333.png?format=raw

Image + Simplexy source extraction: http://trac.astrometry.net/attachment/wiki/SimpleXyVsSdss/sdss%2Bs1333.png?format=raw