If you mainly play with high-gain distortion, then EMG actives will do the trick; if you regularly use anything else, they're not so great IMHO. Perhaps it's just me, but I found that they don't bring out your dynamic attack half as well as passives - but, again, with high-gain distortion, it doesn't matter quite so much. As Elklander said, try out a few guitars with EMGs to see if you like them, and if you do, go for it.