I personally own a pair of Nike Free Runner reps I bought in Bangkok that I now only wear to the gym. Only reason I bought them was because I forgot to bring a pair when I was there and I decided to save some coin for late night antics. Plus they are neon green so it definitely caters to the generation-y in me.
My recommendation, don't run in them, they are not well constructed and, atleast the pair I have, the insoles and upper dont form to your feet that well. As for walking around and tackling the city, I had no problems with them. I still wear them today to muck around in the gym but definitely not a good choice to rack running miles on a pair of reps.
Some times you want to have a pair of bright obnoxious shoes to rock at the gym but dont want to spend much money and I guess that would be the only reason to buy a rep sneaker. Just becareful with where you source them.