There's no question, you CAN do some good with high rep training, but as the backbone of a mass/strength building program, there's a lot better out there.
I've gained on programs where I didn't do more than 1-3 reps in my sets, and I've gained on programs where I incorporate 25-50 rep sets as well. But, I'd say that from personal experience, it's harder to make good strength and mass gains with more than just a few high rep sets, they tend to fare better for me when I'm working to lose fat or am primarily after improving my conditioning level. I might throw a few in (I respond better with things like shrugs at high reps of 20+ per set than I do low reps) here and there, but it's usually the smaller muscle groups or just a few sets as a "finisher" exercise after doing the heavier stuff first.
Doesn't hurt to vary things up and experiment, but I'd be wary of a high rep plan being optimal for many people who are working to get bigger/stronger in the most efficient way possible!
What he said. Variety shocks the muscle and the brain into steady gains if you do it right but everybody's different. It pays to experiment, get to know your body, then only use high reps on areas that will respond to them without losing mass. I knew a real gorilla of a man once who, every once in a while, did a lighter weight to failure. Sometimes, he'd get up to 50 or 60 reps. He did it for "shock treatment" to break a plateau he was in or just out of boredom. His guns were as big around as my thighs, so I'd say it was workin.'
Another way to mix it up is with slow reps, where you lift around 40-75% of your usual load but in a very slow controlled, motion. You do only two or three sets, taking ten seconds each for the eccentric and concentric phases of the exercise. The benefit is that you are flexed the entire time and it is virtually impossible to cheat by using momentum as an assist. It's great for people healing a joint because it's easy to monitor how everything feels when you are moving so slowly. Your entire workout takes less time, too. Obviously, there are a few moves that don't lend themselves well to a slow rep style but there's not a single muscle that you can't address with it if you get creative.