I bought this about a month ago. Quick answer: its worth it. I bought it because the cat converter on my car cracked, so it was either $200+ for a new one, or this.
Now, obviously the basics:
1. you get what you pay for
2. welding is a skill.
This is a great starter, or to have in the shop for random little tasks. It runs on a 15amp circuit which is a huge plus. Being on 110 it can't weld anything too thick. no solid stock. But to make brackets, repair stuff, and stuff where you can smooth out your ugly beads with the grinder, perfect.
I was psyched after i fixed my cat, and have used it on a few other things. Going back, i probably would have gone for the slightly more expensive one to have more control of the power (its just a low/high switch as opposed to a variable knob) and the better one can use stainless wire. Also I read to not bother with the wire it comes with and buy better stuff, loses and home depot stock lincoln wire.
Also the mask it comes with is a joke, but fine for your first job or two.
