I've used Spectacle for so long that I can't remember how it was to use OS X without it. The hotkeys are tied to my muscle memory, and don't clash with any of the stuff I care about (emacs, iTerm2, Chrome, etc).
Me too. It's awkward when I need to use someone else's Mac and it isn't there. I found some of the defaults did clash with iTerm, though. I use it mainly for toggling between full and half screens.