Here's the advice offered by me in September 2012 to a colleague whose daughter wondered about office suites.
… If ever she needs to work with Microsoft Office formats, without Microsoft Office on her Mac:
Free of charge. Donations accepted.
If not using Mountain Lion: slightly outdated NeoOffice 3.2.1 for Leopard, Snow Leopard or Lion on an Intel Mac is free of charge: https://www.neooffice.org/neojava/en/mirrors.php?file=NeoOffice-3.2.1-Intel.dmg
Current NeoOffice 3.3.x for Snow Leopard, Lion or Mountain Lion on an Intel Mac requires a small donation of £6 or more (less than the cost of Microsoft Office).
If you require support from the (few) developers of NeoOffice, it's more costly – "… £60 … or more within the last year …". Developer responses in this area are excellent (far better than Microsoft responses to issues with Office) so the cost is not unreasonable, but I shouldn't rush to recommend this level of investment to an everyday user of an office app/suite.
A key difference, until recently:
- NeoOffice can read and write
- some versions of OpenOffice.org (in some ways a predecessor to LibreOffice) could read but not write
The current version 126.96.36.199 of LibreOffice can both read and write .docx :-) – I haven't investigated its ability to do so with great fidelity for all uses of that Microsoft format, or other MS formats, but the developers of LibreOffice are generally well regarded.
Try LibreOffice, it's free and should do no harm.
.docx as a default for text documents, see screenshots at http://www.wuala.com/grahamperrin/public/2012/09/26/a/?mode=gallery
If LibreOffice isn't good enough, aim for a reduced cost copy of Microsoft Office.
Some of what's above related to Snow Leopard, which you'll not find on a new Mac, but I'm quoting the broad advice exactly as given in September.
Articles such as LibreOffice vs. OpenOffice, Not Always Simple « Power corrupts in proportion to its disequilibria remind us that some use cases may benefit from this Apache Incubator project. In particular, the closing paragraph:
… I think that OpenOffice might have had a greater focus on MS Office
document compatibility, while LibreOffice has focused on advancing
features. I’m afraid my employer needs are squared directly over MS
Excel compatibility vs. new features.