Thanks. Made this post sticky.
Please add as reply not 1.5 bugs directly in here, but url to other threads (one thread per bug).
Best is to test 1.5 against SVN, or nightly build found at
dev.joomla.org and to report directly to joomla 1.5 Q&T forum the bugs of joomla 1.5 itself.
Do not use this thread to describe bugs, but just to keep overview clear. Thanks.