Mike, I think writers like Greg Bear and Greg Benford are extremely important because there are fewer and fewer real "hard" SF authors who really get their hands dirty with the scientific aspects of their books. These two are certainly titans from that perspective. Unfortunately (especially for those of us in the business who edit science fiction and not fantasy) it would seem the more rigorous kinds of SF are somewhat out of fashion in favor of other things. I would highly recommend the recent books of Robert Charles Wilson and Robert Sawyer to you, if you're looking for cool concepts and interesting science (not to mention deft storytelling).
Thanks for the recommendations, Brian. A quick browse at Amazon leads me to believe that I'd enjoy Rollback, Spin, and Axis, at least.