WPMU Upgrade 2.6.5 to 2.8.6 and Multi DB

I currently have WPMU2.6.5 together with MultiDB for it. I want to

upgrade to WPMU2.8.6 & the MultiDB2.8.5.

I’ve seen the upgrade instructions on: http://codex.wordpress.org/Upgrading_WPMU

Any cautionary notes on how to proceed here?

Thanks