We run lots of randomized test cases for our accuracy, if your prices have been off by more than 3% - please email us at email@example.com with the email address you used on the site. We'll (anonymously) add you to our test cases.
Accuracy is a big focus for us; for example, when we added Esurance, it tested within a 1% margin of error in 87% of cases, and within a 2% margin in most of the rest. (We'll be releasing our accuracy data in a later post!)
I'm especially curious how you are getting within 1-3% on Progressive's rates without running their proprietary credit model.
The only thing we need to do this is just to have the e-mail address that you used on leaky.com and we'll do the rest. So _please_ email us at sayhi at leaky dot com so that we can correct your results.