What do you think of Open Office?
Nothing too special. But it's free.
Is it better than/equal to/not as good compared to MS Works?
I'd rate them about the same, but I think a casual user might find MS Works easier to deal with overall.
Can one have both?
Can I use it to work with Word documents?
Yes, with caveats that there are some compatibility issues.
What are its advantages/disadvantages?
Open source software advocates might get pissy about this but I honestly think Open Office is an inferior productivity suite to Microsoft Office, with the only advantages being financial and theoretical in that it's free and it's open source.
I'm currently using Works 2003 & don't like it very much. also I've had trouble with Excel & Works spreadsheet. Changing spreadsheet fonts often results in having to shut down completely and reboot - this was a problem with Works 2002 & I thought it and various other difficulties would be solved by installing 2003. HA! Further, I can't always copy Excel & Works spreadsheets; there doesn't seem to be any consistency, and I've lost serious info because of this. And anyway, I can't go back & reinstall 2002; it simply refuses to be installed.
Well, you can have such difficulties with any of the software. You may want to give the online suites a try. I've transitioned most of my productivity software to the web, and personally use Google Docs
and there are other such free online options. It takes a bit of getting used to but you never need to worry about the software yourself, and all your files are available from any internet-connected computer.