I work with a software developer who will always say, when I ask him, "Well, how close are you?"
"We're 90% complete." He'll say, every time.
"Wow, nice!" I'll respond, sometimes sarcastically.
Finally, I asked him seriously one time, and he explained, that any projects he leads, they are always 90% complete. This is to motivate them. "We're 90% complete, until we find a bug, then we're 80% complete, but that's okay because once the bug is fixed... or that new feature is added... we're right back up to 90% again!" It's a funny technique that's probably really effective if you're good at fooling yourself.
But you can't say, "We're 99% complete" as a serious little quip, because debugging anything is 90% of the work, when it comes to software. It is trivial to put together something in comparisont to getting it clean of bugs. You may have to rewrite swaths of code just to get something clean. It's definitely disingenuous to advertise your product as 99% complete, when not even half the "real work" is done yet.