I got one of these a couple of weeks ago, and I've got to say that I'm in love with it. It doesn't do anything that another tool can't do better, but for about $20 it does a whole lot of neat stuff for a price you can't touch. The original of this tool is made by Fein, and costs several hundred $. Of course, it's a better tool - but I can promise you it's not that much better. In fact, most manufacturers (Dremel, Bosch, Craftsman, etc.) make similar tools, but the cheapest is about $70.
Replacement and specialty blades aren't all that cheap from most places, but there is a web place called fitzallblades.com that sells blades that you can use on this tool at very reasonable prices.
I saw essentially the identical tool at Big Lots the other day and it was twice the price! Some people don't like Harbor Freight because a)their stuff is all made in China or b)there can be reliability issues. I can't argue with either of those If you can get over the China connection and you're willing to return a tool that doesn't work (not all that common, but it happens), then this is a deal for you.
If you want a tool that sands beautifully, does parallel cutoffs, does "plunge" cuts, removes grout, and grinds metal, then you've got to have this (although the blades that come with it may not do all of this).
Here's a link to the Harbor Freight ad. The sale price is $19.99 (I paid $29.99) and then there is a coupon for 20% off a single item.
Let me know what you think!