Microsoft Office for Mac 2011 now available as a free 30-day trial
Naturally, if you do decide to buy it after trying it out, you'll be able to just insert your key into the existing trial installation and unlock it, without needing to reinstall anything. You'll only need to reinstall if you've purchased Office in a different language than that of the trial.
To run the Microsoft Office for Mac 2011 trial you'll need a computer running Mac OS X 10.5.8 or newer, and a minimum of 1 GB of RAM and 2.5 GB of free space on your hard drive.
Download Microsoft Office for Mac 2011 30-day trial