I've had the Harbor Freight for a couple of months and it's been great for me. I've worked on my own car and a friend's and have had zero issues. Got it for $50 with a two year warranty. I bought a 5" backing plate for it and have never used the 6" one that came with it, so I can't comment on whether it's janky or not. I also haven't used the HF pads, so I can't comment on those. Has worked great with LC foam pads, Buff and Shine MF pads, and Optimum MF pads.
The machine feels at least as powerful as the Meg's unit I tried before. It is loud, but I will say that the machine has gotten a bit quieter as I've used it more. It's about on par with the Meg's one at this point (I think). I usually wear ear plugs though so its loudness never bothered me that much.
Like you, I bought the Harbor Freight model to save some money. I figured that if I start to do a lot of detailing (for friends/family or as a small side job), at that point I wouldn't mind laying out the money for a Rupes and turning the HF into a dedicated 3" machine. I'm almost at that point now, but whether I eventually get a Rupes or not, I have zero regrets about getting the HF over a Griot's, Meg's, or PC. Out of those other three, only the Griot's has any advantages over the HF as far as I'm concerned (the lifetime warranty and 25' cord if you get that model), but I figure if my HF craps out after my two year warranty expires I'll have gotten good use out of it as a learning tool and I'll be more then ready to upgrade then if I haven't done so already.
Anyway, hope that helps. Good luck.
