Okay, I'm getting ready to bite the bullet and order a new folding bike. Not my first bike, but my first folder, and my first bike in a long time. I was showing my spouse a picture of the top contender, and after a remark about how I was "obsessed with this idea of getting a bike", there was some acquiescence, "Well, I guess you're going to do it anyway."
I plan to immediately take it to a LBS and get a basic tune up - brakes, wheels, gears adjusted and tightened properly. I also will ask them for some help getting it fit properly.
I've noticed that most folding bikes, including my top remaining contenders, lower the seat to it's lowest point as part of the folding process, and raise it to riding position when unfolding. Some do this with handlebars too. I tried a friend's folder, and found that it was a bit of a pain getting the seat back to a comfortable height each time. I assume that most of you mark the seatpost in some way to make it quick and easy to find the sweet spot when you unfold. What do you do? Colored tape? Marker pen? Paint?
Any other advice for a new folder owner?