The one thing I will stress in terms of their use is to spare no effort when it comes to brushing them in. I thought that just because I was pushed back into the spruces so well, that I could rely on simply the camo pattern. I was picked off at about 60 yards with the foot-stomping, head-bobbing, and the snorting retreat of the whole herd. So from that point on, I have made it a practice to brush it all in so well that I really wouldn't need any camo pattern on it at all. When I get done, I have to look real hard to find it myself.
Also, pay attention to your background and surroundings. When available, pine trees make excellent surrounding cover. Nothing is harder than trying to make one of these things blend in when you're dealing with mature, open, hardwoods. I won't say that it is impossible to use in those areas, but I generally won't bother using anyplace other than heavy, dense, brushy areas where you actually have to hack your way in to set it up.
Needless to say, your approach trail has to be quiet and easy to use, but not so obvious that the deer start using it. Any old lightweight folding stool works well for a seat. try to figure out a bow stand that keeps the bow in an upright and ready position. My stands came with a gizmo that sticks in the ground and holds my bow in a convenient fashion, ready to grab. Also clean out the interior of any twigs, leaves, and other debris that may make noise when you shift around for a shot.
Beware of having so many windows open that you become back-lit. No direct sunlight access into the interior through any open windows. Where I am set up, I really only have one possible direction to shoot anyway so I only use one window open and then it is only partially zipped down (they make them way bigger than is really necessary). Wear dark clothing. Camo is not necessary just dark colors (black is perfect). You may think you are well hidden, but even the small amount of light coming in the open window will illuminate you and show up your drawing motions and any other inadvertant movements.
Set the blind up long before you intend to use it. Even well brushed in, the deer will eventually find it and it takes some time for them to accept its presence. Once they do accept it, it's surprising how close they will come to it.
Needless to say, you still have to be as scent conscious and aware of wind directions. Even though you are kind of encapsulated, you are not scent-locked.
I found it useful to practice setting up and tearing down my blind a few times before actually trying to use it for hunting. Don't always count on instructions. Some of these have a bit of a learning curve involved and are technique sensitive. It is surprising how some of these need specific folding and twisting motions to get them back in their carrying case. That's not always so easy to figure out when you are in a hurry trying to just pick the thing up, pack it up and head home with it. The little tricks are better learned in a basement or out in your yard.
As far as shopping techniques, you already got that right. Head for Gander mountain, or Bass-Pro, or somewhere that they are likely to have a good assortment of them set up so you can judge for yourself the quality and size.
Most of all this stuff is just common sense that you would eventually think of yourself, but sometimes it is good to have it all listed ahead of time so you don't wind up blowing an opportunity and then kicking yourself because an obvious error was made. I have just randomly thrown down thoughts and ideas without any judgement as to whether they are super-obvious or not. Perhaps others will add on to this list with some things that I'm not thinking of, so it can serve as a set of reminders and a bit of a check-list.