Good basic discussion here. I like riding clipless, too. I've found that the more time I spent focusing on technique, the smoother I became overall. I'd like to try rollers some day - I haven't so far and don't like to have extra "gym" equipment around the house that doesn't get used enough (that's my fear).

One thing that seems to help is riding a fixed gear over the winter and early spring. Somehow, mastering a smooth descent at ~130 rpms and upward can teach the muscles how to "round out" the pedaling stroke. Then, getting back on a geared bike seems to be more in synch for me, if that makes sense...