We've used it at Conditioned Air since we've been in business (March 2004) and have had very few interoperability problems with Microsoft Office. It is an amazing tool set that looks and works as well on the Mac (among other platforms) as it does on the PC. Few of our current customers or vendors use it but (and this is a big part of my point here) that's not been a problem for us – Open Office easily reads and writes Microsoft's .doc/.xls/.docx/.xlsx files.

So why do I care what my vendors use? Three reasons:

1. I hate to see people spend money they don't have to. Conditioned Air has proven, with 5.5 years of real world use on thousands of documents and spreadsheets (and much interaction with our Word/Excel using customers), that most people simply don't need Microsoft Office. Why spend the money, worry about licensing issues, and just deal with the hassle if you don't need to? Maybe this strategy isn't for everyone, but for many small businesses it is just the thing!
2. As Ryan and I do more writing (such as our upcoming ebook on how to do collections in a small business) and sometimes have contractors help us, we find that we want to keep larger projects in one format instead of translating back and forth (in this case, from .docx to .odt and vice versa).
3. When I hire a contractor, the purpose is to make my life easier. I'm paying them to do something that I either can't do, can't do well enough, or simply don't want to do. Receiving projects in OpenDocument format is just one more little thing that helps me.

So why not download it and try it out? It isn't a free trial or anything like that – it is FREE, period. You have nothing to lose and $ to gain!