I love it, but it is *dangerous*. Cthon is right, the left hook/right cross combo is nasty and unexpected.
You can throw it with tolerable safety if you establish your jab first, because the other guy is expecting a jab from your left hand. If he knows you are leading with a hook (as sometimes happens with limited fighters that have no jab and a slow right cross), then you are doomed because he will eat you up with right cross counters.
I still prefer to throw it off the jab though -- double jab, then for the next combo jab/hook/cross. The guy expects the double jab or jab/cross, and the jab/hook combo is really unexpected.
The lead hook gets a bad rap because it is often used out of desperation by fighters without a good jab, which is exactly when it should *not* be used. Its best use is shown by someone like Wlad, who sets it up with a great jab, and then lead hooks you instead of the jab.