iPhone 4 power button was stuck/would not move. Would not work.
The guide was excellent but the #000 Phillips in the kit wasn't small enough for most of the little screws. I had replaced an iPhone 3 screen (kit from some other company) and used the Phillips that came with that kit.
It turned out that the problem wasn't the button, but the electronics so I just cut some tiny circles out of tape to make the button push farther. I used regular clear tape because it would compress the least.
Before buying any parts take the phone apart to see what the actual problem is. I'm fine with eating the $5 for the button, and I will eventually use the driver kit for something else, but I guessed I would need the electronic power button but didn't want to spend the money if that wasn't the problem.