So, bit the bullet and installed the latest Ubuntu with the new Unity UI.
Firstly, the install had a failure right at the end - I think maybe my fault. I did it from the LiveCD rather than the usual upgrade and dismissed some windows I probably shouldn't have, and I lost a lot of settings and installed applications. To be honest, it was only an hour or so of reinstalling apps and I was back to normal, but still a pain.
Anyway, to Unity itself. So far, and contrary to what a lot of people are saying, I've been getting on OK. It has quite a few rough edges, but on the whole it seems to work OK. Some things take a bit longer to do than before - finding apps needs to be improved - if you don't know the name of it and it's not on the launcher there a quite a few button presses to get to the right place. Some things are a lot easier - I like the workspace switcher, and the mechanism for selecting which window of an app you want. I just out that middle button on the mouse launches a new instance of an app from the launcher, which is very useful.
On the whole, some way to go to make it really useful, but not a bad first effort given the short development time.