Well....that all went pretty seamlessly. The only slow part was the installation. Then without actually firing 2010 up, go to
Start>Programs>Autodesk>AutoCAD Map 3D 2010>Migrate Custom Settings>Migrate from a previous release. And with only having to do bugger all customising (well none really), it looked exactly like my 2009. Same menu system (including custom menus) and same toolbars (all custom toolbars) docked as they are in 2009. I was pretty impressed.
Haven't had a real good play with it yet, but it seems to be much faster firing up and loading drawings and reponding to commands and things like Quick Properties.
So.....at this stage I think I'm gonna like it.