I took USMLE step II early and had it on my application. I got numerous comments/congratulations on taking the "both MD Boards" and doing quite well. In fact that's the only thing most interviewers commented on... not my LORs, not my grades, not my class rank. Just taking step I only gives them one data point to compare you to the hundreds of applicants from MD schools.
I don't know if it helped me match or not so take it for what it's worth.
Oh, and COMLEX II definitely doesn't matter. I didn't take that until late Feb.