I tried upgrading from 3.8.4 to 4.0.1. Everything went fine, but in the end i get:
Security Alert!
init.php still remains in the /install/ directory.
This poses a security risk, so please delete that file immediately. You cannot access the control panel until you do so.
When i then delete init.php and press Next step, i am forwarded to:
/install/finalupgrade.php?step=6 and i get this error:
Warning: require_once(./install/init.php) [function.require-once]: failed to open stream: No such file or directory in /home/st/htdocs/forum/install/upgradecore.php on line 41
Fatal error: require_once() [function.require]: Failed opening required './install/init.php' (include_path='.:/usr/share/php:/usr/share/pear') in /home/st/htdocs/forum/install/upgradecore.php on line 41