I use OfficeSuite Pro 7 on my Nexus 7. It does word processing, spreadsheets, and presentations/slide shows and included a bundled PDF viewer. I also use a Belkin bluetooth keyboard/tray that essentially looks like a laptop and when you pop it open, you can slide the Nexus in where the monitor would be on a laptop. The keyboard is comfortable to use for extended typing sessions and since it is bluetooth there aren't any wires. The only problem I would ever have is occassionally my fingers would brush against the screen and nail the back button. But besides me being clumsy, it works super well.
However, I did end up getting a Chromebook to go with my Nexus 7 because I got tired of squinting at the small screen. I think it would probably work a lot better with a Nexus 10 as a full-on replacement because of the extra screen size...that or I just need to get some glasses lol.