I'm answering as best I can as Andy is busy at the moment moving house and I don't want your post going unanswered:
As of right now the answer is yes.
You can download the October theme and it works perfectly well with Mambo 4.5.2.3 and the latest Joomla release but with all systems things change. Next week sees the BETA release of Joomla 1.5 and with this comes a massive change for Joomla. It's basically a brand new code base and with that will come challenges.
To quote Andy in a previous post:
I have already tested some of the templates and they all work fine in 1.5. The caveat is that you have to enable "legacy mode" in 1.5. You have to do this for any 1.X template though, and it only 'adds' 1.0 compatibility, it doesn't mean you can't use 1.5 features in legacy mode.