It's a pretty good system for maintaining a sharp edge on a blade that is already profiled to match one of the preset angles -- 30 or 40 degrees. You still need to know the basics of how to sharpen, basically, how to raise and remove a burr.
If your edge doesn't match the preset angles, you'll have to reprofile the edge so that they match. That process can take quite a while with the stones the set comes with. You can add diamond rods, but then the cost starts to rise quickly.
The new Ken Onion Work Sharp is about to go on sale, so the old Work Sharp models will likely be appearing for sale soon at low prices. It's a small, portable power system that is fast and easy to use.