I bought the Arduino Micro at a Radio Shack that was closing out everything. It's in the official Arduino (arduino.cc) packaging, with part # A100053.
I had the same problem as described above - On Mac OS X 10.7.5, with Arduino IDE 1.6.3, the USB port didn't show up as an option.
I thought I was using a "regular" USB cable, but when I changed to another one, the USB port option did show up in the Port select, and everything was able to work correctly.
I was actually rather surprised, not knowing that there was a difference in USB cables. Once I got it working with the different cable, I even went back and checked again with the original. Yep, it didn't work. Back to #2, everything working.