The only one I'd call a gimmick is PCB copper amount (within reason). I don't think it makes a huge difference on mobos - certainly when paired with decent cooling.
Solid caps, ferrite cores, higher rated components against ESD and certainly IR3550 PowIRstage ICs can all be measured. They do have substance, but it's relative. An office machine probably wouldn't get any use out of them (and would be binned anyway after a few years), but for enthusiasts they are nice features.
I've certainly had a few boards where the caps have gone after prolonged overclocking, so I like solid caps. It's also only really the UD5 that has a big price jump due to the excellent IR3550 PowIRstage ICs. It's not like you're paying a huge premium with these features, it's just a nice easy way to know what you're getting.
I don't like excessive marketing as much as the next guy, but I don't think Gigabyte are pulling a fast one here. The theories behind each added thing are known in the electronics circle. It's not like Gigabyte are claiming anything that breaks the laws of physics here