Is it worth it? I am on Office 2000 and think the upgrades to Outlook and Excel could be worthwhile,
I don't have 2010 but am running 2007 and have done since it was launched. I really like 2007 and have found it a big improvement over 2000. At a guess 2010 will include all the improvements I enjoy. I found the upgrades on both Outlook and Excel very useful and I guess all of that and more is in 2010.
BUT BEWARE
No one has mentioned you may struggle to find other users who are on 2007 or 2010. I find that even three years after 2007 was introduced we still have to to backwards convert all documents which are being sent out to our customers as the vast majority do not have the more recent software. Now we have got used to this but it can be very frustrating, you can do all your work in 2007 / 2010 and then have to save any copies for distribution as a backward conversion to, for example, Excel 97 - 2003. All the fundamentals of your document will still work but there may be bells and whistles you have used which are not available to the recipient. This has definetely led to errors within the business as people make changes to docs and save the wrong version etc. etc.
Obviously it all depends on how you use your software. I have become used to having to produce two document types, those for internal use which can be saved as 2007 and those which are for external distribution which are saved as 97 - 2003. I have yet to receive a document from an external source which has been saved as 2007!
Users of 2003 and older cannot open 2007, and I presume the same will apply to 2010. I realise why MS do this but it's incredibly frustrating.