I can avoid a long, drawn-out war simply by working my way up the Majesty tree, wiping out the one "troublesome" race, and allying with the rest. This saves me probably 50% of game duration.
Is there a penalty for winning diplomatically? I guess there kind of is, since you're not the lone ruler of the galaxy, but other than less points due to a shorter game, is there any loss? This seems like the easy way out and I see no reason not to go with it in every game. War is totally useless if, with enough diplomatic techs, they all work their way up to Close with me...
Yeah, there's usually that one guy that isn't as easy to persuade, but with allies or non-threatening civilizations as the only other ones left, it's not hard to forcefully take him out. Even if he surrenders to the other civs, they're my allies - not really any harm done.
Well? I'm not sure what to think.