I ride a fixed gear KHS 100 (retail around $400 or so) with a 48 x 17 on moderately rolling terrain between Reston, Virginia and Washington DC. My commute is 21-25 miles each way, depending on the route I take. Once you get used to it, you can go up almost anything in the fixed gear. I have done Skyline Drive (Front Royal to Big Meadows and back), and a few years ago took it to Colorado to do "Ride the Rockies", where the toughest day was a 22 mile climb up Independence Pass-- from Aspen towards Leadville. Great ride! However, the downhills are brutal (I ride 2 brakes for that reason).
Think about going fixed. I found that riding single speed gives you none of the advantages of riding fixed, and only the advantage of being able to coast.
Oh-- and age has nothing to do with it. Although most fixed gear riders are in the lower age brackets, I am in the 50+ category-- and have done over 20,000 miles on it in the last 5 years.
Enjoy your bike (and you're right-- there is something about a red bike--even though my fixed is yellow
)
train safe-