I am a mostly proud owner of Makerbot #1670. Have it tuned and printing well with an 0.5 mm extruder.
Extras currently have installed (in no specific order):
MakerGear Heated Build Platform
Printruder II
Custom HBP holders (to prevent movement)
Arduino Mega Electronics (from Ultimachine), using extruder motor from Makerbot (not stepper extruder)
Custom firmware, started w/Tonokips version
Frosted plastic shields enclosing build area
Axis Z-roids