For release25-maint, probably PCBuild should be used since that is used to create the installer. For trunk/Python 2.6 I don't know what you will use for the release version.
I actually don't know either, yet. I would like to use Orcas, but it's not clear when this will be released; neither is clear when 2.6 will be released.
I notice that Kristjan would like to see a PCbuild8 buildbot.
Where do you think is the challange to get it working? For the buildbot client itself I would use the same stuff as in the WinXP buildbot (32-bit python2.4, twisted, buildbot, pywin32).
I think the scripts in Tools\buildbot might be tricky, along with possible changes to the master.
For the build scripts in Tools\buildbot I made some small changes to the batch files (appended). They look for a PROCESSOR_ARCHITECTURE env var, and if this is equal to AMD64 the build target and one or two small other things are changed from the default. So these scripts currently build the PCBuild process.
That's an interesting option. I had myself arranged for the master to issue a different build command to an AMD64 build slave.
If you want me to go online with the buildbot please send me a HOST:PORT and PASSWORD.
Doing so in a separate message.