Fixies are great, but there are much cheaper, and frankly more fun ways of doing it. Also, there's no need to spend 5-600 bucks on a pre-built fixed gear. Start combing the used bike shops for an '70s - '80s steel bike with horizontal or semi-horizontal dropouts. Strip off all the crap you don't need (but do yourself a favor and leave the front brake on). Ride, and smile.
Besides, both the Langster and Rush Hour come with pretty tall gear combinations for street riding. Additionally, lugged steel is so much nicer than machine welded aluminum (let the flame war begin!).
As usual, Sheldon Brown has all the answers:
http://sheldonbrown.com/fixed/index.html .
For inspiration, check out fixed gear gallery:
http://www.fixedgeargallery.com/And just think, in no time you'll be able to track-stand with the best of 'em, as well as having the most fluid spin of all of your riding buddies.