First off, I feel your pain. It has happened to me a few times and then I learned...
There are some things I just won't buy from HF. Mostly it's power tools I want to use more than once.
I will however buy: crappy screw drivers, drill bit sets, gloves (nitrite and work), rags, dust control (I have their 2hp for 3 years now, good buy), RO sander (another lucky buy), compressor (yet another lucky buy), sand paper, their freebies are good for gift boxes and a few other disposable items.
I did however buy the grinder you are talking about if it's the Orange one. Mine works fine for me, but I am not a professional and it doesn't get that much use.
And I agree, always check the reviews before investing in their power tools. For example: they have a Hercules table saw on sale next month $279, however lowes has a Kobalt for a few dollars more. Since I have a Kobalt Miter saw and know the quality, I'd pay a few dollars more and not get the Hercules (Hercules is also excluded from their coupons).
Also if I were a professional, I would consider all HF power tools throw aways since it would be tax deduction anyway