Office Pro, then 2000, 2003, 2007 and 2010. The latest is the best, most cohesive offering yet. Its not really a bundle of products. I can drop a spreadsheet or visio diagram into a word document and, if necessary edit it from within the document, including changing formulas, if necessary.
The biggest change, as was already pointed out, is in Outlook. A much more "social media aware" application and more discussion oriented rather that chronological email.
I'm also using 2010, though I have to admit I do not see that much of a difference with 2007. My main use of 2007 over previous versions was when I used Excel for BI purposes, and the additional functionality proved to be so much better for us BI folks. I actually went the way of OpenOffice for a bit, until I managed to enroll in Microsoft BizSpark and now can use the full Office Suite virtually for free.