I have that changer, and it works great! I dismounted and re-mounted some 30"x9.5" tires on a different rims with it. Like anything, there is a learning curve. The first couple of tires, I felt like I was wrestling a greased pig. ;D But then I got to where I could remove and install each tire in about 10 minutes.
Like others said, you need to anchor it into your shop floor, or something. And while you are at it, pick up a couple tire irons at the store too. You need more than the single "all-in-one" iron/handle tool that comes with the changer.