It occurred to me as I was pondering this yesterday that your hunting situation dictates a lot of this. For instance, if you are the kind of turkey hunter that ranges over vast areas of public land the idea of a pop-up must seem like the stupidest thing on Earth. I can't imagine trying to schlep mine over the stuff I used to try and cover when I hunted places like the Big South Fork and Dan'l Boone NF. Yikes. I can also imagine coming on some snerd 100 yards from the road set up in one of those goofy things-- I'd have laughed my ass off.
And we have a winner! The same truism always surfaces in the traditional "Run and Gun" vs "Call and Wait" threads that we frequently see. Your hunting style is (and usually should be) dictated by size and type of property you hunt. R&G on a huge piece of public land is probably the way to go. In southern Michigan the land has been divided into small 10 and 20 acre parcels...you just can't afford to march all over your hunting land, upsetting squirells, spooking deer, bumping birds and setting off the woods wide alarm system. Putting your butt in one spot is the secret to hunting deer or turkeys in these small areas and pop ups help facilitate that. As Shaman mentioned, it doesn't matter whether it's a brush blind or your back against a tree...but sit you must in these areas to be successful on a consistent basis.