Ben I did 10:30-something at 2008 Up, 9:30-something at 2009 Down, and 8:57 this year. I don't really buy some of the generally-accepted guidelines for what your marathon time should equate to at Comrades. For example, on the Down Run 9hr00min pace band I have from 2009, it says it is for 3hr43min marathon qualifiers. I think, in general, that's far too generous.
While there will be 4hr marathoners who get their Rowan, based on my experience I think you need to be in solid 3hr30min marathon shape going into Comrades. Your training must lots of hill running, especially downhill for 2012. Then figure a way to do that training and get to the start line healthy. If you can do these things and then run the race smartly, you'll get a Rowan. Key is taking it easy first half. That second half of the Down absolutely hammers your quads. Going down Fields, I recall weaving to try and keep the decline more gradual. Unlike the Up, where walking the tough hills is standard practice, in the Down it's embarrassing to walk downhill.