"The perfect is the enemy of the good"
A phrase that was popularized by Voltaire according to Wikipedia.
It's one I've always liked, I've seen products like Duke Nukem Forever spend years in development trying to achieve perfection when they could have been released earlier and been good.
Linus Torvalds has been known to say
"Release early, release often"1
I recently attended a forum where there was a presentation on Agile software development and it's use in developing a booking system for prison visits. One of the things they did was pushed the product out as soon as they had their minimum viable product and then added features from there but they had a system and it was working rather than spending years in development and releasing it only once it was perfect.
I'm not sure if he originally came up with the phrase or not but he has used it. ↩