(self-sourced i3 not kit) pretty good (once I got it dialed in) mine prints 13x13x15cm, so pretty big doesn't reach the full build size but works great. I managed to remove most z-wobble- and the backlash is still a bit bad, but i can just modify CAD models to be slightly bigger by 0.2 to 0.4mm on the Y axis, and my models are fairly bang on. looking forward to upgrading from j-head to e3d v6 and a a heat-bed to try to print ABS,
also need lighten the bed to eliminate backlash, I would recommend somebody self build a printer- at-least once to learn. its pretty rewarding once you have something that works in the end.