For 90% of folks, Open Office will serve them as well as MS Office.
I prefer it for generation of resumes, as I can author the resume in OO and then export easily to .pdf and .html. I export to .doc, but check to make sure it is still happy.
Work requires MS Office, though. Too many company-developed VBA apps, too many docs with comments, etc. I always keep a copy of OO handy at work, though, in either Portable Apps flavor or on another work machine. OO will open corrupted/old/whatevered MS Office documents long after your version of MS Office cries out, "No mas!"
Frankly, unless you have requirements that necessitate MS Office, run OO.
There are several pros/cons of both, but I find the semi-auto word completion in OO to be just spiffy. It even learns as you go, so your specific jargon then becomes part of its vocabulary.