I think everyone has to decide what they think is acceptable from a knife regarding things like blade play and such.
But it is very important, as Chuck has put so well, that you have a good "evaluation" tool set when deciding these things.
One of the reasons I got into knife making is that I thought it would be a great way to learn about knives. Man, have I ever learned a lot.
I recommend to everyone that they read Terzuola's book, The Tactical Folding Knife. Just look at what goes into constucting modern tactical knives, and you'll look at your knives and the places they come from in a different way.
Chuck already mentioned that a thousanth of an inch in a washer can make a big difference 3" infront of it. All machined parts are made within tolerances, an acceptable range that a part's size can (MUST!) be made to. A washer may be a thousandth out, the blade's tang may be out a thousandth, a screw may be out a half a hair, and there's some of your play. The tools making the knife parts operate in tolerances themselves! Drill bits have a tiny bit of wobble. All machines have tolerances themselves they work in. This is why adjusting a screw a hair can make such a big difference sometimes, and sometimes a knife may need to be sent back to a factory for simply a different (yet identically looking) liner or whatnot. Sometimes a dissassembly and re-assembly fixes things, or switching screws into different holes.
Simple knives like my SAK soldier don't have many "issues" as there is less parts and the design is much simpler, as is the riveted construction and such. Modern tactical folders aren't the same at all. So may factors going into them that it isn't surprising that there is a bit of play here or a slightly off center blade there.
Another thing about these $100 expensive knives, that "should" be perfect, is that their materials are so much more expensive than the cheaper knives, as is the construction methods. S30V and titanium is MUCH harder to work with than 440A and brass. A Paramilitary made from 440A steel, a 420J2 lock and nylon handle scales would be much cheaper than the current version. Yet you'd still have some of the 'play' issues, as the lock and screw construction and other assembly methods raise all of the tolerance issues raised.
I'm not saying that people shoul shut up and accept blade play or off centered blades. I really only emphasize Chuck's point that to evaluate such issues, get a good bag of evaluation tools. Reat Terzuola's book, and build a kit knife if you can!
When I first got the Manix and felt the vertical play I was pretty ticked. Pobodys Nerfect.
