First tried it in college on a bicycle. Had a leak, fixed it. Clogged the valve stem once (drilled it out to fix it, remove core, insert power drill, yes it works). Worked until the tube literally blew inside the tire. Garden hose washed out what was left.
Few years later got an old truck. Didn't know much about tires and they started leaking. No obvious leaks so I slimed them. They shook bad at 30 MPH for the first few miles until the slime spread around. They did an OK job of masking the real problem, dry rotted tires delaminating. When it popped (parked in the driveway) it looked like it sprayed boogers all over the garage door. This was on the one and only time I ever used slime on a high speed tire.
For wheelbarrows, bicycles and other stuff prone to holes and no need to have balanced, I use it after the first leak as a repair and future preventative. Bicycle note, I don't have any of these new fancy high dollar lightweight bikes. I still run a good old fashion 20 year old heavy weight bike.
I have never tried slime in sub-freezing tempertures.
I consider it good in the proper applications, but not a fix all.