Ingmar Schlecht, the responsable person for 4.1, has announced the first release candidate for TYPO3 version 4.1. There are mainly bugfixes included:

PHP version requirement raised to PHP 4.3.0!
• New feature that allows to override TCA field configuration with TSConfig (by Oliver Hader)
• Usability enhancement: Label tags have been added to many more checkboxes so you can click the label to toggle them (by Ingo Renner)
• Prerequisites to use RealURL with IIS (by Martin Kutschker)
• Some database performance improvements (by Dmitry Dulepov)
• Moved prototype.js and scriptaculous to typo3/contrib/ and upgraded them to their latest versions (by Oliver Hader)
• The install tool can now be enabled by creating a file called typo3conf/ENABLE_INSTALL_TOOL instead of having to remove the die() in typo3/install/index.php after each upgrade (by Michael Stucki)
• Added hook to tcemain that is executed on deletion of records
• Lots of important bugfixes related to M:M relation handling, PHP 5.2.0 compatibility, IRRE, indexed_search and the AJAX page tree

Greets,

Thomas