Well the upgrade itself was painless. However, once I hit the desktop things were a bit wonky. The resolution was wrong (generic drivers so that's expected), but what is even more strange is that about 10 minutes after I started browsing at a low resolution Windows decided to adjust my desktop to 2560x1440... or at least it tried. I ended up with my visible viewport squashed to 2/3 the height of my monitor and centred, with garbled text. Fortunately it was easy to resize it back to a lower resolution again, but then I couldn't resize it back. I should really install some drivers.
I've also noticed some other weird things.
■That the clock/calendar and network widgets overlay the whole desktop in a very faint translucent overlay that creates nearly invisible vertical lines. The other system tray widgets don't do this.
■The volume control, network and clock widgets take several hundred milliseconds to open, which is quite annoying.
■Repeatedly clicking the icons for the network or volume control widgets exhibits unpredictable behaviour. If they are open when clicked, sometimes they will close and other times they will close and then open again. This is something I'd expect from a hastily assembled Linux distribution, not a commercial product that has gone through months of QA.
Note that all of this is without installing updates, just a fresh upgrade.