Please don't mind the mess. I have just upgraded to Drupal 6 and am in the midst of making the theme that I chose off the shelf fit the site better - it will be a work in progress for a little while yet.
I will be posting my thoughts of Drupal 6 in the future as I kick the tires a bit more but for this installation, and hopefully future ones as well, I have used a CVS based install of the core and other modules I am trying. This is also my first test of the integrated Twitter support - w00t!
Observations so far: upgrade was painless but some modules that I use on my personal site are still not supported on Drupal 6, in fact there are a few BETA and DEV modules that I am using as they are not deemed production ready yet.