WordPress MU

hi,
when i want to upgrade, i need to "deactivate all plugins"

does that mean, only the plugins that are activeted for the main wpmu-blog or plugins for all multi-blogs??

Umm.. I keep an identical test site. Any upgrades are applied there first. It might not be best practice, but I don't deactivate any plugins.

Me neither.

I can't image places like wp.com go through and deactivate when they roll in new code.