I don't have a Harbor Freight polisher, and most likely never will, as living in Canada pretty much makes the commute to the nearest Harbor Freight store a non-event.
I will point out, however, that there are production polishing professionals (see Gary Dean) who use the HF polisher day in and day out. His last one went for 2 years. There are also people who have done Youtube videos comparing the HF with the Porter Cable (see 9thgenaccord), and found that the HF has more power than the PC, but it vibrates a little more. Over and above that, there is a guy (I don't recall his name) who actually took one apart and examined every part in detail, and was pretty surprised that the parts quality was extremely good for the price, and good regardless of price.
I have never used a HF polisher, and due to my location, most likely never will. I do own a PC and a Flex 3401, so I don't have a dog in this fight. It does appear from the many, many videos on Youtube regarding the HF polisher that it is a usable tool that can correct paint, and lasts a reasonable amount of time. Gary Dean did replace his after two years, true, but he probably does more details in a week than most home detailers do in a year, and he did NOT re-grease his HF polisher. He has also made the point that you may want to get the extended warranty, which will get you a replacement polisher should yours fail.