Thanks Jason!
That fixed it.
Mavericks on an Early 2011 MBPro is running smoothly. Initial 'boot up' delays as new files sort themselves out, but otherwise noticeable improvements with graphics performance, Safari etc.
Tabbed Finder, better multi screen management and iMessages from Notifications are reason enough for me! The Maps to iPhone will also be really useful!
Frustrated that Disconnect Safari extension now doesn't show avatars at
twitter.com, but hopefully they'll fix that!?
Also, amazed that iLife and iWork were free updates despite buying originally on disk. Hugely impressive. I'm a big Pages fan, and having used Pages 5 all afternoon now, I much prefer it.
Still, I think I'll try to get a little more Ram, just to keep things tickedyboo.
AP