Isometric training results in excellent gains when done properly I don't care what anyone else says. It's a perfect example of The Overloading Principle [and SAID] for the simple reason of using up to 20% of your 1RM for INCREDIBLE time under tension! I'm telling you, if you do it right, your body will grow. Not to mention the fact that isometric strength is great for building stability!
CT agrees with the effectiveness of isometrics:
Oh yeah, don't do what hurts!