I ride a 2006 Dahon Jack (http://www.dahon.com/us/jack.htm)
. I enjoy it because, to me, its like the old WWII jeep of bikes; the simplicity and endurance of the bike appeals to me.
I choose it for several reasons:
1) it folded (security is an issue with me, and I use it to commute)
2) it was simple (7 speed), tough and easy to service
3) designed for urban riding (I live and ride in Chicago)
4) 26" wheel -- I can take it touring if I like, or longer rides. (Looking forward to Bike the Drive this year).
5) normal sized frame. I had no trouble finding and installing a rear rack for the bike. Smaller folders require you to get specialized accessories.
I like Dahons. They have simple and quick folding mechanisms, are sturdy, and offer a large selection of bikes in a wide range of prices that can fit just about any budget. If I was going to have problems getting my Jack (had some trouble with Kozy's ordering it, and got my money back, went to Rapid Transit and they kicked ass), my fall back bike was a 20" wheel. Sometimes I wish I had gotten the 20" wheel as the full size folder can get in the way -- going in and out of doors with it, and revolving doors are not an option. But otherwise I love it.
Dahon makes a nice bag to put your bike in if building (home or workplace) security gives you a hassle about dragging a dirty, oily, gunky bike inside. The new bags they have now seem much better than the old ones (I have one of the old ones) and they are defiantly worth the $60 bucks.
Also, if you get a U lock, you'll have some fun trying to find a place on the bike to store it when riding that doesn't interfere with riding or folding. In the end, I strap mine to my rack. Plus parts of some of the Dahons (Jack, Espresso, Marineer -- just about any 26" wheel size) have some fat tubing for the frame, so you need a lock with a longer U to work with it. Granted I hardly ever use the lock, cuz I can fold it, but sometimes I use it (Like the Chicago Bike Show this past weekend)
Hope this helps. Ask me any questions you like.