Turns out, there’s a plugin called InstantUpgrade. I’d been using it before WordPress started including that feature in their new versions. My experience has been that feature doesn’t always work. I’ve been several versions behind because I didn’t want to face the prospect of a manual install.

Here’s the way I finally upgraded automatically without using the WP tool. I can’t guarantee it will work for you. It worked on 7 blogs with different WP versions flawlessly and one more almost flawlessly (I can’t seem to access the Edit Posts page anymore):

1. Make sure you back everything up first.
2. Install the InstantUpgrade plugin.
3. Deactivate all your plugins except InstantUpgrade.
4. Go to the InstantUpgrade admin page.
5. Select your preference for HTTP or FTP install (HTTP worked fine for me and doesn’t require entering additional info)
6. Upgrade to the latest version.
7. Log back in.
8. Reactivate your plugins.
9. Check to make sure you can still access everything.

Also, I found that some plugins won’t automatically upgrade. What I figured out it that just about all of them upgrade just fine if you deactivate them first.

Hope that helps. Use these directions at your own risk. They didn’t work perfectly for me and might not for you either.