I must say that most people think the W7s are overrated is because everyone who owns one loves it so much and they build up such a hype. Most people can't afford one so the hype builds up even more because they can't hear it personally only knows how other people love it so much.
It's a extremely well built sub, but the price tag keeps people away from it. I've heard a W7 powered by a Phenoix Gold 1200.1 or something in a 2.2c^ft tuned to 30~ something in a Civic hatchback. That thing pounded like no other, Im sure that there are other subs with potential like that and would cost less money too, but anyone who buys a W7 usually aren't dissapointed with the subwoofer.
I myself love my IDMax, it hits low and has really good SQ. And only cost 1/2 the price :-D