I have quite a few tools from Harbor Freight and have had very few problems with any of them. My tool box is like the who's who of quality tools with Snap-On, Mac, Matco and Craftsman from top to bottom. I know the importance and difference of quality tools. With that being said, I have NEVER been disappointed with Harbor Freight's Pittsburgh brand of impact sockets, hammers, pry bars and other non precision hand tools.
However, my experiences with electric and air operated tools from Harbor Freight has been a little different. They don't seem to be of good enough quality to even constitute the low price unless you are planning on using it for a job or two and anything beyond that is bonus. Like a finish nailer for instance. If I was doing some molding work in my house, I wouldn't think twice about paying $20 or so to buy a nailer to speed the job up and make it easier on me. For that investment, if it works after the job is done, its just a bonus. I wouldn't pay a ton of money for a tool like that because I will most likely never use it after the job was complete since home improvement and wood work is not in my skill set. For stuff like that, Harbor Freight is the place for me.
Now for something that I plan on using on a regular basis, I wouldn't waste the money. I'd just spend the extra cash on a quality machine, wait until I can afford the quality machine or live without it.