I read Pat McCarthy's Complete Guide To Web Analytics Solutions: 2007 Edition; a good and long post worth looking at.

My only comment - I would not put ClickTracks in the same category with Omniture, Visual Sciences, Coremetrics, etc.  There's solutions you have to pay for - but don't require huge outlays of money - but that are generally, very good - like ClickTracks and those that do require a lot of money to implement, like Omniture.