I have two or three of the full size ones that I use regularly, and one of the compact models that fits right in the trunk of my GoldWing. The lid from a box of computer paper makes a great target holder and I can get all I want at work. I usually use the Shoot-N-See targets with them.
I like them, they are cheap and pretty easy to setup. They'll take a number of hits from a 22 and still stay together, larger caliber hits will take them out pretty quick though. As Hardtarget noted, when the ground is hard, they are tough to get in the ground. I found I usually still can get them seated by moving them up on the berm just a little.