Worse is Better
dreamsongs.com
dreamsongs.com
For example: Agile (We don't need no stinkin' thinking up front), BDUF (We don't need no stinkin' thinking as we go along), Static Typing (We don't need no stinkin' unit tests), Unit Tests (We don't need no stinkin' static typing) and so on.
Once the idea of "completeness" is crystallized (based on listening to what people want), I think that's when it's a good idea to build it right.
By "building it right", I don't mean to pay the same amount of attention to all features for the sake of completeness. Here, I'm a proponent of the 80/20 rule. Specifically, that the important 80% of the features be implemented first. That doesn't mean ignoring the remaining 20%, just that the rest of it will need to be hashed out later/eventually. An 80% product is enough for a demo/risk-loving early adopters, but ultimately customers want to pay for 90%-100% products.