Pros: Folds quickly and easily. Great for in the city.
Cons: Limited gears
I had one in Beijing and used it daily for commuting about 25 miles round trip to and from work for close to a year. I also took it on a ten day trip through Shandong province. Being able to fold the bike to get it in taxis, on trains, and inside buses made logistics much easier. I had some problems with hills due to the limited number of gears, but that is to be expected.
In almost four years I had no mechanical problems, and only sold it because I was leaving Beijing. I had another road bike that I did more serious riding on (but not to work since it was too expensive to lock up outside), but for daily travel the Dahon bike was great.