A few weeks ago I finally did an upgrade of our intranet, which were running on Microsoft Office SharePoint Server 2003, and upgraded it to version 2007. Not sure if IBM speaks about this upgrade as the one which is "rip and replace" style, but after I did it I don't have this feeling.
The installation was pretty easy, the biggest problem was to find the correct installation set (as we have the Czech version installed, but I had just the English version installation file) but after that it went really smoothly. Just click Next, Next, Next several times and wait a bit.
That was just the first part. After that I had to run an WindowsUpdate (which checked for some new patches) and run the configuration wizard. It ran a few minutes during which it upgraded probably the most important part of database, started the server and some automatic tasks, which upgraded the whole structure. And this part was really long, it took about an hour and after that our intranet has a new look and feel, looks incredible cool and shiny. All without any touch (the question is, if it is correct, but I'm not sure that the branding before was done correctly anyway).
There is just one step in front of me and I'm not brave enough to do it - uninstall the 2003 version (yeah, you have to install new version and then you are able to uninstall the old one). I also lost a few pages, but the truth is, that there weren't any link to them and preupgrade checker probably reported them, I just didn't care too much.
I also upgraded MS Office to version 2007. The cooperation between Office and SharePoint is much better in this version (as described in Fair, Good, Better, Best paper from Microsoft), well, it is about the same quality as I was used to in Lotus Notes (so funny). I'm able to connect my Outlook tasks to different libraries in MOSS and see different tasks lists in Outlook as well as all my tasks from those different lists on one place - in my task's list (something like federated view across more databases, very cool), connect calendars from different libraries (was able to do it in previous version as well, should be nice to be able to connect Quickr calendars to Lotus Notes or see all of them on one place) and connect my document libraries to Outlook and be able to have them offline this way (kind of replication, just didn't find any settings yet).