UltraMon and MaxiVista

Scott Hanselman recently posted about some truly wonderful tools for working with Multiple Monitors, and putting your laptop to work while in the office.  His post can be found here:

http://www.hanselman.com/blog/PermaLink.aspx?guid=fbf0b95f-3fb4-4d46-ac71-8b3158895dad

I'm really thinking about getting UltraMon right away, and the MaxiVista virtual display driver may follow shortly there after.

How many monitors do you think are optimal for development?