I've recently been saying that one big advantage Drupal and WordPress have over Joomla is the centralized hosting of "third party" contributions (plugins/extensions/modules). Yes, Joomla has the extensions directory, but come actually downloading the software, you get directed to the individual developer's island website to do the download (where you might actually need to first register, are likely to needing to do some digging to find the actual download, etc.).
Our friends at Joomlatools are advising against updating Joomla to the latest version, 1.5.17, and remain at 1.5.15 (1.5.16 was released in between, but was quickly sperseded by 1.5.17 due to another problem). Version 1.5.16 introduced a mechanism that will disable a plugin automatically when it runs into an error condition.
Instead of throwing an error the plugin is disabled and prevented from executing under normal conditions. This can lead to a site visitor experiencing unexpected behavior or worse the site could go down.
And once again, I have changed the platform under my personal site. Why? Like we say in Holland: "Gewoon, omdat het kan" ("Just because it can be done") :)