As always I tested out the install on the latest version of virtual box. Download and installation appeared trouble free until I tried running a network app - there was no network connectivity at all.
Cue a flurry of trying alternate networking settings. No joy at all. Then just to ensure the past few months hadn't all been a nightmare, I tried an older virtualbox install of ubuntu (Ubuntu 10.10) This refused to start with a warning that I needed to install the latest Virtualbox extension pack.
Downloading and installing the extension pack fixed my 10.10 vm. I then deleted the natty vm and reinstalled it - just in case I'd broken something else in my hacking about in its config - and it all just worked.
My classic test applications of kwrite and abiword installed correctly. So I then installed nevernote, which has broken installations before now. Installing it caused various whinges from the package manager about it being a poor quality package, but it did install and run.
One problem about running natty on virtual box on OS X is that it claims that the hardware is inadequate to run Unity, the new web interface, leaving me with good old gnome. Which is fine, but I'd have lkied to have a play with Unity ...