I agree with Joe Keith--there are some great advantages to pop-up blinds. My friends and I have spent hours and hours building "natural" blinds, and had very little luck. They don't help with your scent, movement will still get you busted, they can't be taken down and moved, they take much longer to build than a pop-up takes to set up.....they have practically none of the advantages of a pop-up.
Blinds aren't magic--they are a tool, just like your bow, arrows, etc. Learning to use them properly gets you the best results. We've had great results with them, and as best I can tell the deer here are as wary as any. We have one of the biggest populations of hunters per capita, and one of the longest seasons--they have a reason to be nervous.
'Course everyone has their preferances. For the last few years mine has been a pop-up blind. They do have their limitations--they need to be set out at least a week or two before season starts, and left out if possible. They cost more than a natural blind (well, sometimes). They need to be set up properly, and in some cases need to be "brushed in". Compared to the rest of the "work" I do for hunting, this is a piece of cake.
Chad