Just updated to snow leopard which took around an hour. Looks like it worked ok except for a few apps that no longer work 
(expect compatible versions soon enough).
One issue I did come across was that random icons were missing from the desktop / applications / finder side bar etc.
A normal reboot or two didn’t seem to fix it
The solution after a quick search seems to be to delete com.apple.desktop.plist and com.apple.dock.plist from “User>Library>Preferences>” which means the dock defaults back to default which is annoying but at least files will have icons again.
A quick reboot/restart and all was back to normal for me.
