I have several---haven't carried one for years, but haven't decided to get rid of them quite yet. I suppose, for me, I find a Leatherman to be superior simply because the driving tools are actually square-edged and not rounded. I remember attempting to help somebody put a desk together once at work with my SAK Farmer and the polished/rounded screwdriver just seemed to glide right out of the screw heads when they started to get a little harder to turn. Look at true screwdrivers--you'll never find a high quality one with a mirror polished head and radiused corners. Yes, you can square them with a file, but its annoying to need to. Same is true with the Swiss Multitools (I have a Spirit) and I just find that the slightly "rougher" surface finish of a Leatherman makes for more go (with admittedly less show) when I actually want to use one for something. The replaceable bits is also a feature which just really floats my boat, I like being able to zip open the pouch on my wallet and pull out a hex, torx or square drive when I need one. Now there's absolutely no denying that you pay for the rougher finish in terms of tools/blades that can be a good deal harder to pull open than a nice Victorinox, but I've come to the conclusion that I'd rather have to bear down on the nail nick a little harder than be cursing the tool the whole time during use. The mutli-surface (one of them diamond) file on my Leatherman Charge Ti also is vastly superior to any SAK file I've ever seen. I also, personally, have far more use for a pair of pliers than a corkscrew.
In SAK's favor, I think--though very similar--Victorinox (can't really speak to Wenger) really nailed the saw a little bit better than Leatherman. For a start, the SAK teeth are straight as opposed to the rear-pointing, pull-saw setup on my Leatherman models, and this really is superior when using teeth as large and aggressive as these little saws have, it's just easier to get a cut channel started. Also, I'll agree that the SAK scissors are a little better than the Leatherman's, though neither is my choice for true precision, and I seldom need scissors in the normal run of things.
Now, as to the "real knife people don't carry SAKs" argument...well, that's just false. I suppose I can, however, relate to a certain disinterest in them, based PURELY upon the fact that a SAK really is the beige Volvo of the knife world. Serviceable, sensible, very pleasant and polite and civilized in a pleasantly dull sort of way, and absolutely devoid of any kind of personality. I love one-hand opening (assisted or flipper is even better), high end steels, G10/Micarta/carbon fiber/titanium/exotic hardwood and all the rest, and get about as excited about a red-plastic handled knife (the aluminum ones are slightly better) with 420HC blades as I would about drinking a light beer. Now, I can just hear it: the bubbling assertion in somebody's fingers that...let's all say it together...knives are just TOOLS to them and they don't go in for all of that enthusiast stuff.

I smile because it's BS and you know it. If you're a member of an internet forum about knives with hundreds or thousands of posts, you're an enthusiast. I can almost guarantee that you do not have an equal number of posts on "socket wrench forums" elsewhere on the net, nor that you regularly pop into "power vac forums" just to see what's going on. So, admit it, you're fan-boys too.
All of that said, however, the basic truth is that people like different things, and the NEED that some people exhibit (I'm not pointing fingers at anyone specific, just throwing this out here) to have people see things the same way they do exhibits insecurity and lack of confidence . There are plenty of folks who have as little interest in my knives as I have in their SAKs, and we all spend our money where we want to spend our money when we can. The best SAK makers have been delivering satisfaction to a very large segment of the knife-buying public for longer than anyone on these boards has been alive, and will continue to do so long after we're all gone.