12th June 2014:
I haven't tried grayscale yet, but I'll update this when I do.
9th April, 2011:
At first, I was a bit confused about how to make grayscale the default printing method, so that I wouldn't waste loads of ink printing things in colour. But, this is in fact possible to do via the settings for the driver. It's just not immediately obvious. Check out the link to the Ubuntu forum below - in one of my posts there, I described how to do this.