For those of you recommending name brands - I currently have about 20 angle grinders and have gone through about 15 more in the past few years. I tend to use them real hard, and burn them up.
Here's my best to worst brand listing - best is at the top:
1. Metabo - Strong running, great features, and you can't kill them, expensive - I have 2 of them and will buy more
2. Makita - smoothest running of all, very tough - I have 5 of them - probably best overall value
3. Milwaukee - Tough grinder - I have only had 1, so difficult to compare
4. Hitachi - Good grinder, good value - similar to Makita, not quite as smooth - I have 3
5. Porter Cable - Great Value - tough grinder a little noisy - I have 2
6. Bosch - Noisy, they use straight gears, overheats under load, easy to burn up - I only have 1 left, won't buy anymore
7. DeWault - Run smooth, powerful, prone to overheating and blowing breakers - I have 3 - probably won't buy another
8. China Brands - Harbour Freight, Others - I have a couple that probably still work but I don't use anymore - they are fine for occasional light use - they won't stand up to hard continuous use.