They are ok for tools or equipment not used much. Such as at home on the weekends or one use items. I got a nice auto darkening welding helmit for less than $50 and a paint spray gun for $40, a neadle scailer. The items I'm happy with.
What I don't like is it's all from China. But you go to Sears, Home Depot, Menards, etc. and most of the off brand odd ball tools are still From China. The above store just charge more.
I have used several Harbor Freight tools, with great success, for years. I've also seen pure junk sold by them.
IMO, the cheap tool on the truck almost always trumps the fancy tool you can't afford to buy. Many times, it is the blades / bits / accessories that make a tool perform, more so than the tool itself. For example, I have probably spent three times as much on bits, than I did on my roto-hammer itself.
There are some tools too important for you to compromise on, or take chances with. I might take a chance with an umbrella - but that parachute needs perform 100% every time!
I dislike the temptation to judge items by brand name alone. Almost every "quality" manufacturer out there has a few products that are disappointments.
I have a few items from Harbor Freight, and for the most part I am happy with them. Bought a 10" sliding compound miter saw for 99 dollars about 7 years ago, it still works, not as fast or as prety as a DeWalt but the dewalt is about 500, and I am not a carpenter so there is no way I would use one enough to pay for the dewalt. When I worked in a textile mill I bought 2 sets of the Pittsburg Forge combination wrenches, used them for years never had one to break. I think they are too big and thick to work on any newer cars with, but they worked for me in that job. I bought a 125lb Russian made anvil for less than 1 dollar a pound, the chinese version was 1.10 per pound. Just as has been already said some tools are worth it and some are not.
Life is tough, Life is tougher when you are stupid
There is a Northern Tool Supply store right around the corner from the condo my mom owns in Fort Myers. I was visiting in October and November so I walked in one boring day. I got all kinds of cheap China stuff to take home, and so far am pleased with it all. Best value for dirt cheap was the carbide unibit set for under $20 bucks and the several multimeters for $1.95 in the discount rack. Christmas gifts. I have no problem dragging a $1.95 multimeter into an attic. If I forget it up there so what. Please no safety speeches, it will never see any voltage above 240. Got a good working amp clamp on meter with a large jaw for under $20 bucks. My Fluke cost more than 10 times that amount, and it didn't make 10 years so we will see which one was the better value in 9-1/2 years from now.
Although I would stay away from their power tools (unless it's something you would absolutely use only once in a blue moon), their hand tools are starting to carry lifetime warranties. Since I work a lot in situations where tools can walk off, I like the low prices.
It's like my cheapo pocket knives; if I loose an $80 Benchmade, I feel really stupid. If I break or loose my $1 made in China knife, I pull another one out of the drawer and keep working.
A couple years ago I got a job that required a few custom bends in 1-1/2" RMC. Because most of my work is either residential or control/instrumentation stuff, I didn't have a bender that would handle the job. I was going to rent one for the job, but Northern Tool had a hydraulic pipe bender for sale for less than a 2-day rental on a Greenlee would have cost me.
Sure, this thing isn't even remotely close to a Greenlee in build quality, but for a tool that might only get used for one small job, it's hard to justify shelling out $$$ for the "Made in USA" version. If I was bending rigid on a regular basis, it would be a different story.
Cheap tools have their place, particularly for "one-off" jobs, or if you want a tool that you can modify to do some strange function.