I was very pleased the the ballscrews and guides. I put together a very stout DIY CNC machine. I should mention though that the included aluminum couplings are very flimsy compared to the main parts of the product. I used them, but have so far now replaced 2 out of the 3 after having them break. I suggest not using them.Here's a pic which attests to how accurate you can get carving oak using a .5mm tapered ball mill.
Thomas S. 
