I think I'm too late to be considered an early adopter, but I did get an Eris up and modified this weekend.
Raspberry pi/Delta Calibration Plugin: Covered in awesome sauce. G28, G29, load eeprom, run calibration, DONE! I can't believe a delta cal has been reduced to something so easy. It used to take me hours to get my Max V2 calibrated for the larger prints.
Raspberry pi power: I stole 5VDC from the LED back lit face plate and re-purposed a 4 pin molex from my Max V3 build and put it on the GPIO pin of the pi. I wound up routing the wire around the USB jack.
Spooler: Hate it, hate it, hate it. It winds up fighting the extruder on multiple retraction prints, and is sketchy overall. I wound up redesigning it (http://www.thingiverse.com/thing:2007564
) altogether and extending the PTFE tube with another PTFE tube to the top of the machine. Now it is smooth as silk, and I have some real estate for a filament cleaner/oiler. The spool now sits firmly on top of the machine where it belongs.
Print quality overall: Outstanding for the price range. The sample blue is OK, but when I put some of my MHPro on there all of the surface issues I was chasing cleared up. It's actually printing pretty close to the quality of one of my Rostocks.