I used to commute with a backpack until the heat and weight just became too annoying. Since I don't need to carry all that much and my bike has no rack I went with frame bags. It works out great. The only drawback is that it takes longer to strip them off the bike when I arrive, and put them back on when I depart again. It's a minor drawback though, and feeling unencumbered in the cockpit is worth it. I'll still use a backpack on occasion though. It's not as bad in the colder months.

Heres a shot of the rig. I no longer use the top tube bag as it proved itself unnecessary.