I currently have both a Dahon Speed and a Bike Friday Crusoe. I owned the Dahon about a year before I got the BF. I enjoyed the Dahon, but the BF completely outclasses it. It really does feel like a real bike. The Dahon always had some wiggle and shimmy when I hit the bars (handlebars, not drinking bars
), but the BF is solid.
You could also look for a used Xootr Swift. They're reputedly very solid.