You'll only ever access the menu to set things up. People always mention it (and it's a pain to navigate, yes), but hardly a turn off!
Worth it, up to you as the cost is enormous, however it's a fantastic monitor, and I'll be sticking with 21:9. 1440 pixels is roughly enough in terms of height (1600 is ideal), the extra width allows for three browser windows or four 80 column text windows. For gaming...others have covered it, little more to say.
The only warning I can give is that for higher settings for demanding games, SLI is a good idea (even then in GTA V I'm jumping between 55-85fps, and 55fps is still horrible, even with G-Sync).