Yep, and like cycling "perfect" (let's not start that debate) circles it is the transitions that you really need to work on. I posted a link above to concept 2's site - they have a ton of good resources and videos on technique.
The most common mistake I see is bending the knees before your hands pass over them. this means that you need to lift your hands to clear your knees since they are already in motion. And it is bad, not to mention awkward looking!