The most exciting improvements in WSS V3 is the fact that all site definitions are language neutral (No dependency on an specific language like 1033) and ASP.NET 2.0 localization techniques are all over places in site definition files. I am really surprised that some of folks walk their blog readers through cloning site definitions using STS site definition. STS site definition in all Beta versions IS NOT a good example for reverse engineering, because SharePoint Team is in half way making it language neutral. If you look at folders below:
C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\SiteTemplates
and
C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\1033
You see that STS site definitions spans into both folders and being in 1033 means that part of this site definition is still based on 1033 and is definitely subject to change in final release.