On my recent expidition to DC/MD/VA, I was able to sample both the DFH 90 and Pliny for the first time. The latter isn't a BAD beer, IMHO, but it's far, far, far more sweet than an IPA should be. In the historical context, it hardly makes sense to even call it an IPA, those brews were designed to be very dry so there would not be many residual sugars to spoil (it wasn't JUST about the hops).
I'm not sure if it's a matter of being under-attenuated, or simply how much malt the use, but every DFH beer I've had has been way on the sweet side.
Pliny, OTOH, is an absolutely perfect example of a BIG beer that is attenuated fully and extremely drinkable (well, if you like hops).