I've got that router, bought after much research. Really like it, so far it has been very solid, and FAST. Great throughout rates. It replaces a low-grade business router, so there are some features which you don't have total control over (understandably) because the 3700 is a consumer router.
It also replaces a separate WAP (Netgear WG602v3), and I put a high-gain antenna on that. The wndr3700 has been put in the same place the WAP was - top shelf in my office, which is a small bedroom on the top floor of a 60's 3 bed semi.
2.4ghz range seems to be just the same, perhaps slightly weaker, which surprised me, I thought it might be less, given the 3700 has internal antenna). Seems faster though. I have nothing to compare to for 5ghz, but the range is somewhat shorter than the 2.4ghz band, but that is no surprise - I really wouldn't expect a 5ghz signal to travel as well as 2.4 (although I guess that depends on the power).
I'm intending to put the latest dd-
wrt build on it, and use the USB connection to drive my printer. I'm sure if I connected a powered USB hub to it, the router could drive the printer and a NAS, its a powerful unit. DD-
WRT will also give me more control.
Hope that helps.
Muts.