I love my Liberty 3:



As is from BD, it was the best bang for your buck road bike I was able to find at $600 when I was in the market (not sure about now). If it helps, I'm 5'8" but have a 29" inseam and I had to buy the 43 cm to be able to stand over the frame. On a traditional frame, I ride either somewhere between a 48cm and a 50cm.

Backpack commuted on it (though I have a dedicated commuter now so I take the Liberty to work less often now), and rode a few centuries without any problems. When you buy it, expect to have to do some assembly, tweak the drivetrain a little bit and to take the wheels to the LBS to get properly tensioned. The latter is particularly important if you're going to be commuting on it.

Note that mine in the picture above does have a few modifications from stock form.