For some time, Pat and the team has been working behind the scene on migrating the old udev to eudev maintained by Gentoo team and the result is now goes public. This is another big change for the upcoming Slackware release 14.2 besides other big changes that already pushed to the -current branch in the previous big batch update. The transitions should be smooth as long as you install the new packages (eudev and libgudev) first.
Pat also used this chance to upgrade icu4c and boost to the latest version, which *may* break third party packages since most of them will link to icu4c and boost library. You may need to recompile those packages in order to work again.
nmap 7 which was just been released is also included in this release along with many other new packages such as php, hplip, harfbuzz, lvm2, and many others.
I hope this update also fixed my problem with xorg on my Hybrid GPU laptop. startx failed due to segfault in the intel driver.
Do please read the ChangeLog before upgrading.