I am extremely happy with my Bike Friday New World Tourist which I've had for 5+ years. I don't think the ride is any harsher than my old touring bike with full-size wheels, but I do think the smaller wheels result in more precise turning and control, which I especially like when riding in traffic. I've got an old touring bike and mountain bike that I almost never ride anymore because I like the ride of my NWT so much. I commute on it nearly every day. I've done loaded touring on my NWT in 7 countries on 4 continents, including mountainous areas as well as unpaved rail-trails. The folding ability has enabled me to take it on transport which doesn't normally permit bikes. I've never had to pay a thing to take it on any planes, and I've flown with it on 10 round-trip flights already. A few of those trips were just brief visits to cities or regions where I probably wouldn't have bothered to take one of my other bikes due to the hassle and expense of dealing with airlines. So far, at least, I haven't had any problems with airport security or damage.
I've only converted the suitcase into a trailer once, but that worked extremely well and is surprisingly easy. Still, I prefer to tour with panniers and have always been able to find a place to store the empty suitcase when needed.
One small piece of advice if you order a BF is to get high pressure tires. The tires I originally ordered could only hold moderate pressure and they gave a sluggish ride. When I switched to high pressure tires, it made a huge difference.