I did buy one of these back in October, it was about $120, the prices have gone up and Amazon was cheaper than eBay. I finally got it out and fooled around with it for about 2 hours yesterday.
My initial thoughts are it is clever and has some potential, but also frustrating. Plastic and aluminum parts, with expanding connectors so it takes some work to convert it between functions, but is secure once fastened together (more Erector set than Lego).
It will cut brass, sort of, but that sort of is largely where the frustrating comes in.
With a little more effort I think this could be a decent little lathe for simple turning or for a young person. Unfortunately it has a fairly powerful, but single speed motor that runs at a very high speed. The hand wheels / lead screws are awkward and jerky, but functionaal.
The tool holder is a huge fail, being a sort of T nut with just a screw to hold down the cutter (even hokier that it sounds, literally just the cap of the screw barely holding the cutting bit). It comes with what looks like a 1/8" pre-sharpened cutter.
I have more hopes for it as a small drill press with X/Y table (milling machine is way to grandiose a term).
Now for somebody with some technical skills and some real machine tools, I think it could live up to my low expectations. I am going to make a simple (but better than a screw) tool holder for it, and see if it can't do a little better. Being able to vary the speed of the motor would be a huge improvement, this thing screams like a dentists drill. A variable speed Dremel motor would be quite useful here.
There are more expensive versions of these, some costing several hundred dollars that possibly might be better, but at that point just buy a HF mini-lathe.
Still if you have kids and want to get them something to learn with, and are willing to put in a little effort, for $100 this little machine isn't a complete waste of time.
If you want a mini-lathe, buy a mini-lathe.