I had wanted a heavy bag for a long time, and had just been putting it off. My husband got this for me, went and got the bags of sand, and at my suggestion based on other reviews, a funnel. He started filling it when I was at work, and he texted that it was going to take forever because the sand clogs the funnel (cut the end off, by the way for a wider mouth). He had about half a 50lb bag of sand in the base, and that took him about an hour. I got home and I watched for a minute or two. I got a butter knife and a chair and sat next to him. You can fill this on your own, but it is easier with two; one to scoop and one to stir. The trick is to use the butter knife and stir like you're mixing frosting in a bowl. It is easier to have someone to scoop because you can get a 2 cup scoop of sand down in about 15 seconds and it helps keep your stride and pace to not have to stop. Now, if you don't have a helper, I discovered on the last bag (of course) that if you cut the bag open and let it sit a few hours, it dries just enough to make it go that much faster, and while my bags averaged 25 to 30 minutes, the last bag was completely in the base (yeah, I used the full 250lbs of sand...I figured when they said 230lbs, they meant the base if full at that amount but it looks like I could probably do another bag but based on the instructions, I wouldn't) in about 15 minutes. So the slightly drier sand makes all the difference in the world! I use this bag regularly. I can't speak to sliding around with the impact. I have mine on carpet in the corner, and I have an old yoga mat that I hate rolled up and in between the base and wall, so it sits solid and takes impact with no trouble.
Rating: [5 of 5 Stars!]