Column based db anyone?

[eluser]johnwbaxter[/eluser]
I've got a CI application that deals with a relatively small db. It looks like i'm going to have to scale it up to a db with millions and millions of rows and a fair few columns too.

I was going to have a look at column oriented dbs and wondered if anyone had any experience in this area.

I'm looking at http://en.wikipedia.org/wiki/MonetDB at the moment and wondered if anyone had any thoughts / experiences to share?