Cool prints Bobbler! Good to see you're having a lot of fun with your printer.

Regarding dual extrusion; lots of people will say that it's 'impossible' because dual extrusion is basically dual the problems.. and if you don't have one extruder under control then its almost impossible to get them both under control.
But it looks like you already have quite good settings going on.

The only problem that still remain is that extruders keep leaking plastic and with big parts this means that they leave drops of one color on a surface that's the other color.. Makerware has these purging walls for that and S3D will supposedly come out with some good dual extrusion settings in a few months.
Same is visible in your print: some white drops of plastic on the edges of the blue surface; but depending on your model you can wipe/sand this off (or use Makerware with purge walls for now)