Quick releases are less thoroughly tested releases which are made more often than numbered releases. They are not guaranteed to work, but may solve some issues and introduce new features. For the absolutely most up to date release, checkout the SVN copy (but that involves downloading SVN tools and so on).
Checkout the code as follows:
svn co https://neuralensemble.org/svn/brian/trunk
If you are using the SVN version, we recommend you checkout to a permanent directory, and add that directory to the Python search path, e.g. by creating a text file mymodules.pth in the Python/lib/site-packages directory with a single line pointing to the directory where you have checked out Brian to.