I rode the Dynamic Sidekick 7 speed shaft drive folder for about 3 weeks. I bought it with a 30 day trial offer. The people at Dynamic are very good to deal with.
I really liked having an internal gear hub, and being totally chain free by having a shaft drive was wonderful.
So, why did I send it back? Mainly, it did not fit my long legs, without going beyond the seatpost min mark. I did not want to do that long term. The new model will have a one inch longer seattube, and so it should fit me, 6ft tall with long legs. I could have added a ButtBuddy to gain 2 inches, but I did not want to invest that in the 7 speed bike. I would only get one with the Nexus 8 speed hub. I needed a lot more low range, without giving up on the high range. The Nexus 8 speed will do that for me, (307% range instead of 244%). They did not have the 8 speed available at the time, and I did not know that the 7 speed would not work that well for me until I tried it.
The bike also did not fold well, did not stay folded, and rarely stood up by itself. I used it as a "lay flat" by only folding the handlebar post, lowering the seat, and rolling it into the backseat of my car. The folding is nothing like a Bromptom or Dahon. Dynamic wanted to have Dahon make frames for them, but Dahon was not interested. Dynamic was receptive to my idea that they add a lighter layflat to their line. This bike was fairly heavy, 32 pounds.
I may buy the Crosstown 8 instead from Dynamic. It is a full size, non folding road bike, but it is only 27 pounds, and has a wide gear inch range since it has 700C wheels. I would opt for the lower range drive, but you can read their gear inches and decide for yourself. If I add folding pedals, and remove the front wheel, I could fit it in my backseat as a layflat. I drive a very small 1991 Civic SI hatchback that I bought new and really like.
I would definitely recommend a Dynamic bike to anyone who wanted a very clean and low maintianance bike. If you get the Sidekick, I would recommend upgrading to the 8 speed. You would have a bike that rode and maneuvered well with its 20" wheels. I did not notice any extra drag or loss of efficency compared to chain drive. It can work well as a layflat, but remember it does not fold well.
For a folder, I am now considering the 2008 Dahon MU XL Sport, it's twin, the Novara Fly-By at REI stores, or the 2008 Dahon Curve SL. All have a Shimano Nexus 8 speed hub and chaindrive.