To be honest it didn't take me long to find the device I wanted. Blue Microphones have an excellent reputation and their chrome-retro styling has a certain 30's space opera feel that I found appealing. The fact that they were getting consistent good reviews for sound quality also helped a lot. Most of their devices aren't that portable, but I found the one I wanted very quickly: the Snowflake.
Sound quality's good so far, and it'll work with my Macs and my PCs. It is a little larger than I expected, but not too large, and the base doubles as a carry case for the USB cable and as a clip to hand the mic off the back of my PC. I do like the way the microphone folds into the base for travel, and the ability to twist the head to point where I want is definitely a plus.
All in all, I'm very happy.
Now to go out and interview some people.