I've been using these for over a year now and they have served me very well. You just have to understand their limitations- the main one being that you don't want to drop them on the floor. The other is that the max weight is 52.5 lbs. So yes, if you're very strong and you like going to failure, you might be a little disappointed. However, if you're an average person like me and just want to get in a decent home workout, these could be perfect for you.
The adjustment mechanism is easy to use and the weight increments make a lot of sense. They start out with 2.5-lb increases with the lower weights and jump up to 5-lb increases at the higher end. You can do anything you would do with normal dumbbells- bench presses, shoulder presses, curls, triceps extensions, rows, flys, lunges, etc