OK, I haven't posted for a while... been busy!
Having heard (over and over) about how cool Master Pages is in ASP.NET 2.0, we got sick of waiting and are going to implement the Microsoft-published Master Pages sample from 2002. The funny thing is, I had already used that on a project way back then - but before I really fully understood the Page class and ASP.NET internals... you'll see a post of mine on that www.asp.net page - and I clearly haven't yet learned about Control.ClientID. D'oh! Removing the INamingContainer attribute seemed like a good idea at the time :)
Actually, we'll probably use the MasterPages: Improved Version by Paul Wilson anyway.
As for the post title - Paul was spot on: "MasterPages is the most flexible and easiest to use of Page Template solutions, and since it was created by Microsoft it will likely someday be in ASP.NET itself."