The only real problem I've heard of is bows inverting, flipping inside out. This is a real problem, especially as bows are marketed as a safe option for beginners. The other stuff, bar pressure, build quality I haven't heard any complaints. Looking at the amount of bows turning up at beaches everywhere, even as new C kites get sold for half price, should speak volumes. Bow's dont make as good windbreaks as C kites!

As for "foils = spongey feel, quicker setup and relaunch, more power per size for the flat ones"
I'd call an ARC spongey, not my FS Speed. Bridled foils and ARC's are too different to be lumped together, and Speed is different to all previous bridled foils. This is where the cutting edge design is at.