planning for WP 3.0 with MU

hello, I’m going to begin developing a new site that will use WP 3.0 mu features. One of the MU sites needs to launch before 3.0 will be released. The primary site can follow later.

Would you recommend launching on 2.9 regular or MU? Which would offer a smoother upgrade and transition?

Is there any documentation on the transition from MU to 3.0?

The tricky peace is that these will be regional sites. NY needs to launch soon, but the primary international piece can come later.

Should I just build the NY site as a standard WP site and then export, install 3.0, and then import?