While most of the big changes are already noted in the Release Notes or in CHANGES_AND_HINTS, there's one addition that it very handy to make Slackware installation easier, which is the new support of HTTP/FTP during installation process. It's documented in the Slackware-Howto in the Slackware mirrors site:
For the network options, you'll need to have a network card that's supported by one of the installer's modules, and preferably a DHCP server running to make the network setup easy. The network install options are to use as your source an NFS server, an FTP server, or an HTTP server (along with an optional port). If you use DHCP to set up, odds are you'll have working name resolution and won't need to enter an IP address to specify the server (but you can if you wish, of course).
The network installation feature is intended primarily to facilitate installing to many machines on a local network. Please don't use it to bog down the Slackware mirror sites.
Thanks to Eric Hameleers for finally bringing FTP/HTTP installation support to the Slackware installer. :-)
So, if you have a bunch of computers to be upgraded/migrated to Slackware and you have a good network connection, this method might be useful to ease your job