Depends on what I'm doing.
If I'm just taking notes or laying down ideas, I write them in the RTF editor of DEVONthink, and store things there. That's where I put my RPG campaign, various odds and ends, etc.
For the odd one-off printed material like a cover letter or fax cover sheet, I use Pages. I don't do anything big or ambitious in it.
For big printed works, I use either LaTeX or InDesign. My cookbook is in LaTeX, which is great at keeping the bazillion recipes consistently formatted, doing the index, cross references, etc fairly automatically. My printed RPG material is in InDesign, which is a lot easier for work I want to do visual design on. For example, I did a newspaper for a campaign for a while, and InDesign was great to lay out articles. When using InDesign, I'll usually write the text in something like DEVONthink or another RTF editor first, then import it.
I have LibreOffice and MS Office (the latter through the MS Home Use program) as well, but I only use them for compatibility purposes as needed. For word processing, that's almost never the case. The biggest need I have are spreadsheets that use VBA.