This does work with TMO and any other 7100 series handheld. TMO will be releasing their OS4.0 handheld software in the next 1.5-2 weeks (word from rep). They are still beta testing and should have newer code than this version. There would be no reason to hold off installing, if you don't mind reinstalling the newer TMO in the short-term future.
You do have to delete/rename the Vendor.xml file from C:\Program Files\Common Files\Research In Motion\AppLoader.
Conan, the O2 theme can be found here
. The instructions on how to install themes can be found here
(looks like you already found it though).