I'd rather have no (eg) wiki feature at all then have a half-assed one.
Because _if_ I feel like the feature might be useful, I'm going to try to use it, and invest time in trying to use it, and only then find that it's not reliable or well-polished after all. The more such features there are, the more chance I'll spend at least some time being frustrated by at least one of them.
One of the joys of really well-polished software is that if the feature wasn't worth doing right (and not every feature is!), it simply isn't there at all, so if a feature is there I can count on it being well-thought-out and well-executed.
Because _if_ I feel like the feature might be useful, I'm going to try to use it, and invest time in trying to use it, and only then find that it's not reliable or well-polished after all. The more such features there are, the more chance I'll spend at least some time being frustrated by at least one of them.
One of the joys of really well-polished software is that if the feature wasn't worth doing right (and not every feature is!), it simply isn't there at all, so if a feature is there I can count on it being well-thought-out and well-executed.