We stayed at Spanish Trails summer 2014 and did not care for it either. Campground folks were nice enough, but not much shade, a good bit of dust (maybe not unique for moab), highway noise, and in a somewhat industrial area. We even left a day earlier than planned.
If it is just a place to sleep while you do other activities all day it is probably OK, but if you are spending several days to relax, it would not be my choice. To each his own.
PS - Don't miss Dead Horse STATE Park, across the street from Canyonlands. It was every bit as nice as Arches and Canyonlands, if not better.