I could have used "stupid" but we'll get to that later.
They suck because they are heavy compared to a comparable buffed tire and they split, but most importantly because they are heavy. Ask most people who are serious about sand riding and they'll tell you that Sand Stars aren't any good for serious torque or horsepower. Anyone who has had a set for a while (myself included) will find that they start splitting right in the middle of the "v".
Let's talk about weight, everyone knows that if you free up unsprung weight it = free horsepower, so why do people spend all this money on pipes, programmers, cams and filters only to throw a set of heavy Sand stars on even heavier SS rims. That is just plain stupid. You can get the same "V" pattern on a shaved tire and still have the same "flickability" of the heavier-molded Sand Stars. Don't take my word for it though, ask around the other "dunatic" forums and you'll quickly see that people stray away from sand stars once they find out what is best.
I agree with you that there's a lot of people who like them - they're not as expensive as Skat Trak's "Edge" but IMO you get what you pay for.