Firebird- you got it. Keeping the cutting surface flush against the work, rather than tipping the tool so that only the outside edge is being used. It's something that's rarely ever mentioned in "how to" articles, but correcting the behavior in myself has probably saved me thousands of dollars over the years. I felt like I was making progress faster by tipping the grinder, and maybe I was in some type of way: but the damage I was causing in doing it that way negated any time I'd saved . Once I realized what I had been doing, I started not blowing through material quite as fast, and I used a lot less Bondo to hide my flaws!

Ryan- I'm using the 3M wheels on my angle grinder with no issues. I'm not sure of their intended use, but I'm just throwing mine on the old DeWalt and watching paint disappear.