Joomla 1.5.15 was released today, three months after the 1.5.14 release.
The update contains two security fixes and a lot of bug fixes. A lot of issues with TinyMCE has been addressed.
There has also been an addition to the TinyMCE editor, i.e. the option to create templates in TinyMCE editor.
An important addition to the system is the added option to disallow users to view extension XML files. This was proposed by Brian Teeman, I believe, and will increase the security of your installation.