I actually used the def:diff model in anger at work recently, helping put together a strategy for the refresh of our viticulture and winery management systems in Aust/NZ.
For the purpose of presentation I simplified it to the ubiquitous quadrant model seen here, with generic sourcing choices for each. The boss seemed to like it ... plus he's turning into something of an evangelist for SOA/ESB himself!
I also came up with another model to help decide on implementation sequence ... I'll work it up a bit more before I publish.