I've had a Slingshot Cyclocross model folder for about a year. At the risk of upsetting people who ride some of the other folders, the great thing about this bike is that it is a full size bike. I originally purchased the bike thinking that I would use it on a tour last summer, and then it would be reduced to strictly a travel bike. What I've found is that I put as many or more miles on the Slingshot as I do on my Trek 5200. The Slingshot is comfortable, handles well, and is quite fast.
Here's the downside. For me, this isn't so much a folding bike as it is a take-apart bike. I ride a 59 cm frame which is one of their bigger frames, and I'm packing the bike into an S&S hard travel case which can be checked as luggage for no additional charge. There is no way the bike fits into this case without essentially taking it apart vs. folding it. Again, this may be due to my large frame size, but I would ask some tough questions regarding any folding bike and how difficult it is to pack into a hard case.
It takes me about an hour to disassemble the bike, and another hour to put it back together. In my mind, that's still a pretty good use of time considering that you'd probably spend at least an hour or two picking up and dropping off a rental bike.
- Buy a SRAM chain with the quick connect link. When you pack your bike, you'll want to break the chain and pack it in a plastic bag or small tupperware container.
- Buy the packing material from S&S. It allows you to create custom wrapping for your tubes to protect the bike. 99% of the paint damage to my frame is from the one time I experimented with how to pack the bike without wrapping the frame first.