Originally Posted by denny
it took a couple of days to get it working right, but I guess it's a fairly unusual set-up.
No. It is the standard way of doing this. I have the same setup and it works fine.
Remember, Twinview is a nvidia extension. It was invented in the days when two displays was still rare and special, and support was not present in all X servers and windowmanagers.
Now, it is common, and supported as standard. There is no need to still use Twinview, except it may be handy in some very special situations (e.g. when you do not really want two screens, but want projector output out of a laptop, or similar)
At work I have ATI cards, and thus no twinview. But the above setup still works.