WORKAROUND (finally!!!):
sudo editor /usr/share/X11/xorg.conf.d/50-qxl.conf # insert the following: Section "Device" Identifier "qxl" Driver "qxl" Option "ENABLE_SURFACES" "False" EndSection # save + reboot with QXL video This was suggested on a mailing list for a downstream Jessie distro, thanks to those guys. The original reference: http://lists.freedesktop.org/archives/spice-devel/2012-November/011479.html I don't know if this is a real solution (strange that xserver-xspice is missing) but with this fix Iceweasel and apps now seem to run at full speed in my Jessie VM.
