my first time was with a front brake, so it wasn't difficult at all. rode about three miles through traffic to work. loved it.

the first thing i noticed/loved was my ability to control speed and balance at low speeds. instead of having to tap-tap-tap a brake to go slowly between/around stopped cars, you just pedal slowly, then a little faster, then slower, etc. It was great-- and fun.
there's no replacing a road bike (being able to go from a 42-17 to zip up a climb, then switch to 53-14 to attack hard on the flat is irreplaceable), but i enjoy fixed lots more.
i ride my track bike 99.99999% of the time, even when a road bike makes more sense. they're fun, fast, make you work, are ninja silent... love it.
my gf and i have 4 between both of us, and i'm building a 5th on friday.