I am overall very pleased with "Bob". I rate it 4 of 5 due to, in my opinion, a small design flaw. "Bob"'s neck is too soft. They should have put a spring or something in there. When you place a hard straight blow to Bobs face, his whole head tend to just bend over.
Overall however, this is a really great item. I only filled the base with water, but I get a good workout. Bob will move around a bit when beaten, but it feels good. The main difference between this and a sand bag, is that you can practice blows in a more natural manner. For instance uppercuts and hooks are far more life like when practicing on Bob. Bob can also stand for front kicks and round house kicks. Bob's soft surface is very life like.
I keep mine outdoors and just put a plastic bag over him. Whenever I feel like it, I just put on gloves (see the MMA Gel gloves from Osaka fast and cheap) and I get a good hard workout.