In summary: very smooth, much better than 10.1 to 10.3 because I didn't try to do it on line, but with an upgrade DVD.
Minor problems with the graphics card driver and monitor but they were easy to fix.

Some niggles with things like DNS but again, it was just a case of redoing tweaks from 10.3 that had been undone by the upgrade.

Rather annoyingly VMWare's 'vmware-mount' command mounts the image read-only, so if, for instance, you need to remove the device drivers that make , you can't.

This is easy enough to get around, however:

Today I went to start Windows as guest in my Ubuntu install of VMWare and, boom, VMWare has broken itself during one of the prior kernel updates (because it doesn't use DKMS or release patches quickly enough).

According to a report, Ben Forta has said:

"The project is currently on hold. There is not enough requisition for the product to continue its development"

Sometimes when installing an AIR application, the installer refuses to proceed with the mysterious 'Error# 5100'.
This doesn't appear to be documented anywhere, but it actually means the temporary file space is full (i.e. /tmp/ on Linux).

Guess the 100meg cap on my tmpfs wasn't enough, eh :-)