I bought one over Christmas, 6040 with:
  • old-style (blue box) parallel port controller (24v PSU and TB5650s on a card)
  • 800w air cooled motor
  • Huanyang 1.5kW VFD spindle controller

It was the bare minimum that you could call a CNC router, no limit switches and kept missing steps on anything faster than a crawl. I replace the controller with
  • GRBL on Arduino Uno
  • TB6600s
  • 36v PSU
  • Some limit switches NO and series wired as pairs for X, Y, Z

Which I would call a marginal upgrade - I wanted the 6600s to take the extra voltage of the 36v PSU. I used bCNC to pump the G-Codes.

Than I milled some stuff: first some air, then some polystyrene, then some MDF (a spoilboard then a dust boot), then some phenol plastic.

Not bad results, quite impressed with what you got for the money TBF.

I was building up to milling aluminium (I also have a 1.5kW spindle waiting in the wings) but accidentally milled the top off a steel bolt (holding down my spoilboard) and by the time I hit the Big Red it had made a pretty good job of carving a slot in the bolt head. So now I'm not so scared of trying that aluminium

So yeah, with perhaps a few cheap mods (TB660s @ £6.50 a pop etc.) I'd say I'm well pleased with it so far!

-Phil