Re: Singe WP or WP Mu??
Given the option and with no impediments in the way you would always want to run the latest stable release of WP. WPMU is now effectively obsolete, and is merged into WP 3.0 thus WP 3.0 is the only WP that people will install after which they will decide whether they wish to run as a single blog (default) or to enable Multi Site mode.
I would install WP 3.0, at a later date if you want multi site then you can enable it (I am assuming that there are no issues enabling MS later having run BP for a while)
