markdown-mode version 1.5 is out. This is a major revision compared to previous releases. The functionality has not changed very much, all of the keybindings are the same, but it is internally quite different.
Most of the changes involve syntax highlighting. The regular expressions have been significantly improved and the corresponding font lock faces have been tweaked (hopefully for the better, but feel free to customize them). Various other small bugs have been fixed and the documentation and website have been updated.
The one change in functionality (which is optional) involves syntax highlighting for embedded mathematics via itex, involving LaTeX-like expressions, and highlighting for bracketed wiki links. This is primarily useful for editing pages on math-enabled Instiki wikis such as xbeta.