I've only played a couple of his courses - one is the aforementioned Legacy Ridge. I sure liked that course a lot better before all the houses were built - but that's not the course's fault. Not too memorable a course to me, although the 13th is a fun hole, if memory serves, a downhill par four with a tree that is rather inconvenient off the tee.
I do, however, remember Walking Stick in Pueblo, Colorado. A fun course that contains some really lovely arroyos that the holes hug and wind around and over. The arroyos are used well, and while the greens aren't too exciting, getting there is a load of fun. But beware the walking stick cactus itself. It's a mutha.
On the basis of those courses I wouldn't want to make a case for Hills as a great designer, but Walking Stick especially is a lot of fun, not especially difficult, and a nice looking course.
Wow, is that praise or an indictment? I guess that depends on the golfer.