The following is a list of known issues with MATE on Slackware:

Wed Mar 27 04:23:24 UTC 2013
If you have dual monitor with NVidia card and set it up to use both monitors 
as separate, you might encountered some freeze lockup. 
The temporary workaround is to change it into Xinerama in your xorg.conf

Sun Mar 24 02:47:56 UTC 2013
If you run into strange panel issues, or missing icons, or theme problems,
please consider backing up or clearing out some of the hidden directories in
your $HOME, like $HOME/.config and $HOME/.cache and $HOME/.local.  If you
switch back and forth between different desktop environments, sometimes those
settings can get polluted.

Sun Mar 24 02:44:53 UTC 2013
A couple of users have reported Caja (the file manager) crashing with an error
message telling the user to run Caja with the --sync option.  Please let me
know if you run into this.  Before doing so, however, please consider backing
up or clearing out some of the hidden directories in your $HOME, like
$HOME/.config and $HOME/.cache.  If you switch back and forth between
different desktop environments, sometimes those settings can get polluted.

Fri Mar 22 16:45:28 UTC 2013
Mate-screensaver in /testing doesn't seem to work -- at least, the locking
feature does not seem to work in my testing.  I tried it with xscreensaver
disabled and also uninstalled but it never kicked in.  More testing is
necessary.

Fri Mar 22 16:44:59 UTC 2013
Help menus and help buttons do not work -- this is a known issue per a MATE
upstream developer and scheduled to be fixed at some point but not in the next
release (1.6).

Fri Mar 22 16:43:36 UTC 2013
Working to determine whether mate-polkit is necessary.  According to upstream,
it is, although it results in duplicative polkit actions when a USB stick is
inserted, for example.  Disabling polkit-gnome in the "Startup Applications"
is a workaround until more testing is done.