There are probably a lot more unsuccessful products out there that have really dreadful code. Is it possible to have a good product and have bad code? Of course. Is your product going to die a horrible death because it has a few bad lines of code in it? Absolutely not.

But you're kidding yourself if you don't think that the quality of your code doesn't have an impact on the quality of your product. Well-factored and modular code allows you to iterate much faster in the long term. Of course, if you need to iterate faster in the short term, then by all means use a few well-placed hacks. But you can't let them pile up otherwise you're hurting yourself.