I use some Harbor Freight tools, along with Milwaukee, Bosch, DeWalt, and so on. In power tools, I've found some of the HF stuff to be adequate, but if you want Milwaukee quality and durability, buy Milwaukee.
Some of the hand tools are likewise OK. I bought an air impact wrench at a garage sale without realizing it was a HF tool, and it's been fine. I also bought a 48" pipe wrench from HF, which I needed for a particular job, and it lasted well enough through that job. The teeth, however, are somewhat dull by now. If I had bought a Ridgid, it would have cost about 6 times what the HF wrench cost, but it would last more than 6 times as long. I have Ridgid and Stillson wrenches that are probably older than me and still good.
The lifetime warranty is intriguing, though, and if you're an Inside Track member, you shouldn't need your receipt for exchanges.