Right off the bat, for a freeware solution, OpenOffice is amazingly comprehensive offering you all the features that you might expect to find in the paid equivalent, MS Office. Let me just say, that if you rely more on Word than any of the other Office tools, then you will find Writer a more than worthy replacement, but if your area of expertise is Excel, then I reckon you might not want to change for the simple fact that you could expect a few unfamiliar controls and making the switch won't exactly make such a difference. (Unless your at a startup walking the fine line between staying in the black and falling in to the red!)

OpenOffice has been produced by a very healthy open source community and will continue to grow and improve, especially if the project gains further support from individuals and companies. If new computers were to be sold with this installed, then MS would have good reason to start shaking in their boots.