I downloaded and installed Microsoft Office 2010 Plus beta version. I have used Open Office and supported it for academic use. But when I started writing and editing my dissertation, I found it is difficult to use Open Office. Not because of its quality, but because of its compatibility. My advisor started using MS office 2007, and it was hard to convert document that he sent me with comments. Also, RPI provides its dissertation template in MS Word and LaTeX format. Too bad.
Main reasons why I supported Open Office were (1) equation editor, and (2) more powerful spread sheet function. Open Office has much better equation editor than MS Office 2003. MS Excel cannot handle large spread sheet (over 250 by 250 matrix, not sure about exact number).
I found that Office 2010 has improved at these two points. (Actually, there were improvements in Office 2007. I didn't pay attention on Office 2007 because of disappointing reviews of it.) And its beta version is free till October 2010, when I will be long gone from school. So, finally, I decided to go back to MS Office, taking advantage of the free beta version. After that, I may go back to Open Office, or not...
So far, I am satisfied with Office 2010. It has all functions that I need. Equation editor works really fine. However, its interface is not so user friendly (to me). It is similar to Office 2007: whenever I use Office 2010, I am amazed how well they could hide tools that I need most. Its tool bar requires significant amount of time to get used to it. That's my only complaint. Good thing is that you can customize tool bars more freely. I will write more about it when I found something.
You can download the beta version HERE. You need MSN ID or Hotmail account.