The first attempt revealed that in order to get a full melt, much higher temps were needed (265c @40mm/sec) just for PLA.
At normal PLA temperatures (~215c) the bottom layers contracted due to the filament not being fully melted and acting more elastic.
Next, we tried out the .8mm nozzle with .6mm layer height. Some quirks that come with fused filament 3D printing become exaggerated with larger layers, while the fixes seem to be more forgiving. At least you don't need a magifying glass to see the layers!
Extruded filament (PLA) measured at exactly the nozzle width. We haven't tested the other nozzles, but I can only guess the machinging quality is the same.
E3D's volcano heater block mounts the heater cartridge vertically to increase the melt zone. It heats up about 4 times faster than the standard orientation (pictured left). Nozzle heating is so fast, that about as soon as the printer is done homing, it's ready to print.
Comparing a standard .4mm nozzle to the 1.2mm opening on the Volcano.
It's interesting to see all the mechanics of plastic extrusion exaggerated like this. Taller layers and faster prints are a great thing to have when you need it. The wider extrusion width also provides much stronger parts. It's worth noting that you'll probably need to calibrate your firmware's PID settings and z-offsets for the new heater block.
In conclusion, this is turning out to be a must-have upgrade. Even with a standard nozzle size, the improved heater block is outstanding.
edit: As of now, you can only get down to .6mm nozzles that fit the Volcano heater block from E3D.