Free weight workouts is a great way to exercise. Obviously there are certain exercises you cannot complete with dumbells alone, but overall using dumbells is the best way to exercise and maximises your lifting power. There is a lot of difference when using barbells, machine weights and dumbells.

As this is the body building forum and not weight loss or body weight training, the home user with a set of dumbbells and a bench is not going to be able to do as much as a similar home user with an Olympic barbell set, rack/powercage and a bench.