I made some progress tonight converting from Paul Wilson's MasterPages to the built in ASP.NET 2.0 MasterPages. I got the Default.aspx page converted and working on Windows, it was pretty straightforward given that Paul modelled his version from early specs for the real thing. Now it will just be a machanical repetitious task to update the remaining pages and skins, but not tonight, I'm spent. I tested on mono at demo2.mojoportal.com, it did load the MasterPage but something went wrong loading the rest of the page content as you can see. I'll follow up with that and see if I can pin down the problem.
I've been getting very excited learning about the Web Part framework. I know I said I would pace my changes with mono support but I think what I will do is keep a separate branch in step with mono support until the mono support catches up so I can move forward taking advantage of 2.0 ASP.NET features. Some of them are just too compelling to wait and besides it will take some time to make the changes and figure out exactly how I want to do it. Right now I'm thinking the Web Part model will replace the existing implementation for Feature Modules.
I definitely will try and help implement some of the missing mono features if I can, or at least provide testing and feedback for the guys who are doing it.