Windows 32bit Family XP RTM - 5.1.2600
XP SP1a - 1106
XP SP2 - 2180
Server 2003 RTM - 5.2.3790
Server 2003 SP1 - 1830
Server 2003 SP2 - 3959
Vista RTM - 6000.16386
Server 2008 Beta 3 - 6001.16510
Windows 64bit Family XP 64bit RTM - 5.2.3790.1830
XP 64bit SP2 - 3959
Server 2003 64bit RTM - 5.2.3790.1830
Server 2003 64bit SP2 - 3959
Vista 64bit RTM - 6000.16386
Server 2008 64bit Beta 3 - 6001.16510
I installed the recently released Office 2007 SP1 Technical Preview update on top of Office 2007 Enterprise Edition running on Windows Vista Business Edition. Here's some quick info about it:
The Microsoft Office Cache folder (MSOCache) does not get updated with any SP1 bits; only the \Program Files\Microsoft Office\ folder is partially updated. New files have varying digital signature dates (as well as older version numbers for some of the older files) ranging from May 30th, 2007 all the way up to July 23rd, 2007. Naturally the dates will all change as this is not the final build of Office 2007 SP1.
Not much more to say about it at the moment as I did not notice any usability or user interface changes on a quick glance. All in all, a very smooth update to an already smooth running Office suite.
Update: Additional information is available at ZDNet (including a claim by a user regarding some of the more detailed changes found in SP1). (via Ars Technica)