MS Office 2007 Service Pack 1 really makes a difference!
I finally decided to install Service Pack 1 (after I had SP1 Beta for months) and I really see the difference - it affects not just Office applications but also whole Windows Vista system!
Because I am "bad" user (I have large Outlook PST files up to 8GB) and I use up to 20 open applications/instances/windows with several services up-and running - I had a problems with performance (and installing Vista with Aero support on my HP nc8430 with 2GB RAM/200GB HDD 7200 did not helped at all.
So, to summarize: I had more responsive Office applications - primarily Outlook and my Word does not crash every time I close a document, any more :-).
I am also happy that a lot of improvements was done in MS Project, but I did not have time to check it (holidays and family :-) ) as my colleague Luka is writing in his blog: http://live.mscommunity.net/blogs/lugospod/archive/2007/12/17/influence-of-microsoft-office-2007-sp1-on-microsoft-project-2007.aspx