Here some additional information concerning the new beta release (official release notes here unfortunately are very outdated) .
There are some possible Regressions compared to 2.38 (bugs, what appeared after release of SeaMonkey 2.38). It would be great if some users would do bug triaging with the UNCONFIRMED ones from the list. (1)
🙂 But, of course, we do not only have possible regresses, but also real progress, several Bug-Fixes.
(1) A Bugzilla-Account is required to proceed these queries. Please consider that SeaMonkey might be affected by bugs and bug-fixes for Firefox, Thunderbird, Core and others, none of the related bugs will appear in resulting bug lists.