Yes, they do work!
There are both temporary and permanent effects. The permanent ones take a couple of years. You will get both length and girth. I've gone from 5 1/4" to 6" in permanent girth over the years, and from 6 to 7 1/4" in length. There are also a manual method of stretching that seems to work pretty good. Basically, grasp your dick around the neck and rotate it around 20 times one way and 20 the other while maintaining outward tension. Do 2-3 times per day. This stretches the ligament.
The key to pumping is to not overdo it. You are expanding the spongy tissue cell to hold more blood. Do it every other or 3rd day, NOT every day. Keep the vacuum reasonable. One variation is to use a very low vacuum, but keep it on long periods (sleep with it on). Of course you'll need to shave near the pubes to maintain vacuum.