I just got my CP-1 today. I can testify to the problems with installation. After trying to force it with the "body weight and pillow method" I managed to gash my palm open. Not fun. So busted out a nice sharp Spyderco and shaved a tiny amount (less than a millimeter) from each side of the dovetail keeping the blade perpendicular to the dovetail. It slipped right on first try after that.
Overall, I would say the CP-1 is definitely worth the 50 bucks for those having preamp problems with the original. I have gone through 2 original preamps already after they both developed annoying static. The knobs on the CP-1 feel much more solid, no static at all. The headphone jack is very nice too, works very nicely with my Sennheisers.
-v13