When I commute, I'm usually running late (or taking the long route to get extra work in). Either way, I usually am going fairly hard. I typically don't ride on bike paths though (except at night), and if I'm agressive, it usually takes the form of swearing at asshat cagers. That's just me though.
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Bikes: 1996 Eddy Merckx Titanium EX, 1989/90 Colnago Super(issimo?) Piu(?), 1990 Concorde Aquila(hit by car while riding), others in build queue "when I get the time"