I use MEK for thinning Tamiya primer, along with using it for cleaning the paint-contact parts of my Paasche H airbrush when I have run most lacquers and enamels through it. There are a few acrylics that don't do anything but gum up when they come into contact with MEK, but its a really good all-around cleaner for most paints from airbrush parts.
I keep it in sealed relish jars for use at my bench, so the vapors aren't released in any large quantities...and only released when I open the jar for a few seconds. When airbrushing with the Tamiya primer, I don't shoot huge clouds of it (or anything else I airbrush with) like I see a lot of guys do, so vapors aren't much of a problem there either. I protect my hands from it when digging my airbrush parts out of the cleaning jar by wearing latex gloves. They're simple and effective.
The relative dangers of MEK in comparison to other common solvents are only worse in urban legends. They all require a certain degree of handling precautions, but one is not really any worse than the others. The "MEK Substitute" they used to sell in hardware stores was a result of those urban legends, and actually turned out to contain materials that were even more toxic. As far as potential physical damage to various materials goes, I have actually found Acetone to be the worst of all of them. Tried various solvents once to try to remove a silk-screened placard from a 1:1 aircraft instrument panel, and none of them even touched it...including MEK. Acetone, on the other hand, almost instantly removed the silk-screening, along with some of the grey epoxy powder coat underneath it.
So, count me in as one of those who are all for it.