Well... A little update.

With PHP 5 and Artio JoomSEF my Community Builder registration confirmation and AcaJoom newsletter sign up no longer work, so I'm falling back to PHP 4 again.

Gah.

Good news!

I installed 2.2.3 (removing 2.2.2 first and doing a clean install just to be sure), and Eureka! It works again!

I can now use PHP 5 without issues. CB and Acajoom registration and confirmation work without great. And I no longer need to have custom redirects for / and /index.php. JoomSEF correctly redirects these on its own to my home page.

As a side note, using phpMyAdmin I exported my jos_redirection table before uninstalling and then imported it again after installing so as not to leave any of my old redirects undefined. I probably wouldn't have needed to do so if I did an in place upgrade, but I wanted a clean slate.

Happy Thanksgiving!

=)