OpenOffice.org

Only good. I use Open Office to augment MS Office 2004, as OO is able to open files that MS Office 2004 cannot. The MS Office interface is "slicker", but I find MS Office will occasionally crash. OO never crashes. Go for it.

I find OpenOffice is a little sluggish and unlike dgauthier, it does crash a bit with me, mostly in the spreadsheet part it has to be said. Even then it always does offer to recover the files that were active at the time

Despite that it's free and gives you a certain level of compatibility with other office users (but not perfect) so I'd say you run no real risk from trying it out.

You might want to take a look at NeoOffice - it is a different iteration of the Office alternative application which is a bit more polished and Mac like.

Also note the main development of Open Office "forked" into LibreOffice after Oracle acquired Sun Microsystems. The developers are concerned Oracle will not support Open Office to the extent that Sun did. LibreOffice can be found at http://www.documentfoundation.org/

Same here. OpenOffice on Mac seems unstable, much more than the Windows version. It also mangles equations, fonts, and object placements when importing/exporting to Word and PowerPoint formats. If you are going to share files with others, the compatibility will be mediocre at best.

But hey, it's free! Try it out and see what you think. As others suggested, you might want to try some of the independent OO-based versions.