Like Stefan, I use a mixture of free, open source and commercial software. Generally, I'm happy to pay if the software is better than the alternatives. This includes Photoshop, CaptureNX, Keynote and MarsEdit.

I also use TextWrangler, MacVim, Eclipse etc as I find these fit all my textediting needs better than commercial alternatives such as TextMate or Forge.

We also have MS Office at work as whilst OpenOffice and iWork have made great strides in compatibility, they aren't fullly compatible with some of the spreadsheets we get from clients.