Ah - I'd forgotten about the content token change. I thought I recalled a deprecation warning when using the old approach, but I can't seem to get it now - on 2.2 or even latest 2.3dev, with developer-level debugging enabled - so I guess it shouldn't be an issue at the moment.
Looking back, I tried to ensure maximum compatibility for this in Decaf by checking whether the new function exists and falling back to the old token if it doesn't. For any themers who want to do the same, you can see my changes (the frontpage.php and general.php changes are probably sufficient for you) on github.