Hey Paul,
I'm not much of a landscape guy, but my general feeling around here is that beyond the occasional polarizer or ND (for slowing shutter speeds to aid with silkier water), most around here don't use filters that much.
Several of the tech-cam guys prefer to take multiple exposures and blend them as opposed to using ND-grads and the like.
Sometimes you'll see some center-filter usage as well, but that's really just for fall-off correction.
I think the great color you see here is due to all the "umph" these cams have in their files as well as the amount of care that many here put into both capture and processing... especially the capture phase. Some of the more experienced members here walk away with files that need very little technical work on the file, leaving the only "pushing and pulling" in post to the creative enhancements... which gives a great file in the end.
Just my impressions, probably not gospel.