I have the Harbor Freight version. Like most HF tools, it's loud and gets warm pretty quickly. But, I believe the other knock-offs (Craftsman, Dremel) have the same problems. At $30 (with coupon), it's pretty good value for the money.
This tool is unbelievably handy on many DIY projects. It is great for cutting into drywall & door jambs, and the scraper can get lots of stuff you'd normally have to hack hours by hand. Like Joe said, it's great for plunge cutting or working in a confined space. I needed to make a hole in some 2x4s in a very tight area last month, far too tight for a hammer and chisel. The multitool made short work of it.
The blades definitely don't last too long. In fact, the three blades that come with the kit are almost as expensive as buying them separately!