Well, it depends. Depends on one's preferences, I guess. For me, speaker systems which are calibrated only towards the sweetspot feel increasingly unnatural. It breaks the spell for me when I move out of the precise soundfield by standing up or moving one meter to the left. Again, it's not like that when I listen to real instruments. I can't move "out" of the precise soundfield when I listen acoustic instruments. Moving around only changes the perspective (and the timbre I hear).
But there's always a catch. For the most precise imaging, a defined sweetspot is always necessary, I believe. I just came home from auditioning the Beolab 50s. In narrow mode, they are stunning speakers. Magnificient. Nothing more to say, really. But would I be happy with them at home, in the unlikely case that a) I could afford them, b) I could convince my girlfriend that we should invest more in new speakers than in renovating the house? I'm not sure. Standing up, the spell was broken. And for me, that's kind of a downer. Which means that the speakers that interest me the most are either line sources or CBTs, oversized electrostats, enormous horns, tall dipoles à la Linkwitz 521, or omnis - all speakers that can project a soundstage over a much larger area.