I'll keep it brief and direct. This bag is just great. Super easy to fill (water for me) and assembly when done. Its solid as you like once the nicely designed skirt locking and strap system is all cinched up.
Does it move when struck? Simple answer is yes it does.
Does this detract in anyway the bags functionality? No! No it doesn't.
I've had people of many different size and strength whacking the torrent with kicks and punches and whilst it does of course have movement, for me it's in no way excessive.
Now 100% I can knock this over with jumping in power teeps and if i throw a double mid to highkick the built momentum could allow me to again knock it over but all in all I'd recommend this bag for anyone that simply cannot have a bag hanging solidly.
I am a Muay Thai practitioner and therefore throw my kicks with more impetus and follow through than other martial arts that utilise point style flicky striking. The one con i will highlight is that it's not greatly suited to knee strikes as most knees bring you into close range and therefore the potential for feet crushing injury caused by the base wobbling back to flat is real in this instance.
Summary: Hanging bags are the traditional and still best method to practice solo striking, simple. That being said if you don't have a place to solidly hang one this is the very next best thing. Expensive? Yes. Worth it? 100% in my humble opinion.
LoL, so much for keeping it brief! :)