A friend asked me to upgrade his blog to WordPress 2.5 RC1, which I had decided to avoid until it’s actually released, so I tried it out on a local copy of this site running on my MacBook Pro. Unlike Drupal 6, I found the update was completely painless and didn’t break any of my plugins or themes.
I’m very cautious about upgrades. I always try it first with a local copy of my website running on my Mac. I don’t use MAMP; I use the built-in version of Apache with PHP5 enabled and MySQL installed.
After I verify that it works on my Mac, I try a test site. I create a subdomain like test.mysite.com, copy my files to the test directory, and make a copy of the database. I then try the upgrade on the test site. When I’m satisfied that it works, I simply swap the test & main site directories. I usually turn off the ability to post while I’m doing the update, to avoid having any stories or comments posted to the old site.