Our team, 3324 has been working with the replicator 2x for a little over a year now. It has become a major part of our workflow moving from CAD design to aluminum manufactured parts. We're even using our machine to create custom wheel spacers some other actual robot parts.
We almost exclusively print in ABS for the strength upgrade. Early on we had some issues with warping but we've mostly solved it all with a combination of frequent and precise plate leveling, increasing bed temperature slightly and applying an acetone/ABS slush mixture onto the plate before each print.
We've started sourcing our ABS from IC3D - it's a local (to us) company creating high quality filament for cheaper than I can find anywhere.
http://www.amazon.com/IC3D-1-75mm-Pr...&keywords=ic3d
http://www.ic3dprinters.com/