I am really satisfied with the metal Plus : auto levelling, nice volume, reliable and tweakable. And now I have updated with metal hot end and I'm planning to go with the double geared extruder as well.

That's what makes Printrbot so great : they don't just sell machines, they also provide stuff to keep the machine current with upgrades.

http://3dprintboard.com/showthread.p...al-Plus-prints