Pros: Cheap
Cons: Everything else - limited travel, poor rigidity, high friction, very intolerant of dust.
Drawer slides are what you would use if you wanted to build a very small machine, on an incredibly small budget.
The best way to use them is to use them in pairs, so that as you extend one, it's closing the other. This addresses some of your concerns.
Imo, you'd be much better off with a skate bearing on pipe machine. Read every build thread in the Joes 2006 machine.
My recommendation for you would be to build something like a Joe's 2006 machine, and do it as cheaply as possibly. Use an Arduino and GRBL for control.
You need a machine, in order to learn what you need to know.