My neighbor has a mid 1970s Phoenix, from one of the other big government-owned Chinese bike factories. All parts are interchangeable with the FP bike. It is a decent ride, but the chrome quality is poor (everything except the chainwheel and cranks needs full re-chroming; you'll literally cut your fingers on the peeling chrome from the rims). You will have to work very hard to mess up the frame. It's stiffer than my house.

The folks at Flying Pigeon LA do some smart mods to theirs to make them run better and be more durable, including new cranks and hubs.
It adds a few hundred $ to the price, but it sounds like the increase in reliability is worthwhile for some.

Also, Schwalbe makes the Marathon kevlar belted tire in 635mm (28" x 1.5" english). It apparently works pretty well, except needs a lower pressure than rated to run well on those old-style rims. The Schwalbe Delta Cruisers work very well for a lot of people here, though they do not have Kevlar. I've been running them for 2 years on a Hercules sports with no flats.