It works, I love hate the stuff. I used to run it religiously but then I started changing and swapping my own tires .. it's a disaster and tire shops will hate you when you change your tires ... I now pack it with me as if I get a flat I can't plug 100% I will add it to aid the plugs. And if you live in the cold it will freeze and it will make your machine feel like you are running on square tires
one of the first things i did was slime the tires on the wolverine and my grizzly. my300 articcat tires were always soft. i slimed them and have not had a problem with them since 2005. i am a believer. but yes they do make one hell of a mess when you go to change the tires.
We used to use slime when we all had lower ply tires (carlisles, ITP mud lites). I was running carlisles on my Outlander and they did help. Since most of us have switched to a high ply rating tire, we skip the slime. Good to have in the bag though.