Re: How do people handle upgrades on live sites?
Plan for the upgrade and pick a time when your site traffic is low.
Let your users know ahead of time that you’ll be down for maintenance. Even with just a few users, letting them know is a courtesy, because if they do visit while you’re upgrading and they don’t know what’s going on, they may eventually leave because they think things break all the time.
Yes, we backup ahead of time. Really. With large site where it would be impossible to ftp things without it taking all day, just backup files in a different location on the server. Optimize & clean up the db while you’re at it. Who wants to back up spam?
Some of us with large sites do not deactivate all plugins and then reactivate later. With hundreds or thousands of blogs, it’d be a nightmare.
At some point when your site is very large, you’re just going to have to get used to doing some things command line (ssh). In many ways, it’s easier.
The moving of the them only occurred during BP 1.1. Shouldn’t have to do it next time. But! Paying attention to core changes helps you anticipate these things in advance. You have to do your homework.
The maintenance mode plugin may not work properly in MU. My fave trick, if I*really* wanna keep people out, is to toss an index.html file in the root. I can still get in the backend, but many users just can’t figure out they can type in these things without a link there. 
Man, this means I have to write up a blog post about it now, doesn’t it?
