I rode my friend's Barbie-pink Brompton folding bike in Boston. I was impressed. It rides very well and folds so small you can almost put it in your pocket. Small enough to bring in to places with you rather than lock it. And when it's folded, it rolls. My Swift Folder doesn't roll. If it were a present, I'd take the Brompton of the Swift Folder. But the Swift Folder costs much less (about $800 versus $1,400) and is made in Brooklyn.
This Brompton bike was fully equipped. Fenders, rear rack, a dynamo for lights, a bag that attaches to the front, and three speed internal hub plus a 2-speed derailleur giving half speeds. The latter seemed a bit excessive at first, but Boston has more hills than NYC. I used all the speeds. Boston is also a fabulous biking town because it's so damn small. I miss biking in Boston.
Folding bikes are great, once you get over the goofy way they look. But hey, unless you're a beautiful woman or a man in a suit riding an Amsterdam-style bike, you already look goofy riding a bike.
Are folding bikes as good as a full-sized bike? Well, that depends on what your full-sized bike is. For all the idiots riding around the city with too large aluminum-framed mountain bikes with straight handlebars and knobby off-road tires, well, the city folding bike would be a nice step up.
My complaint about folding bikes is that they're a very rigid ride. But mostly that's not because they fold but because they're hard aluminum and not soft steel (though that lack of the traditional triangle shape must also play a roll). The handlebars are also a little smaller than I would like. But I'm picky about bikes. And very sensitive.
I bought my Swift Folder as my New York City bike before I lived in NYC. I could keep it my girlfriend's apartment. It served me well but now does not get ridden much. It now is a guest bike for short guests.
And if the choice was folding bike or no bike, I would have no hesitation.