I already moved all our comps over from Firefox to Opera today. Was a little difficult to get the bookmarks over, but it so far appears faster.
Opera's note-taking feature was a great tool in the writing of my book. Also, their email client is quite advanced - it uses "tagging" rather than the ancient "folder" paradigm. The built-in IRC is also quite handy if you ever have use for IRC.
I think of Firefox as a "developer's browser" and Opera as a "productivity browser".
I just migrated my Firefox bookmarks to Chrome after uninstalling Firefox. I’ve never tried Opera. What’s so great about it? Does it let you have drop-down search engines like Firefox?