I can't explain it either, but my commutes loaded with gear are just as fast as my weekend rides without... maybe I have "commuter legs?" Ride today was pleasant, for a change. Only got squeezed once at a stop light, but we were going like 5 MPH, not a big deal.
Yesterday, I got buzzed really close, the guy had to pass and turned off immediately at the plumbing store right there... when he got out, I recognized him as one of my friends, and called out to him. Come to find out, I told him later on Facebook "that was me" and he was so embarassed! He thought I was just yelling at him for his bad driving, and ignored me (which I was). Gave me a good laugh.