Customer-impacting bugs were identified and fixed before they reached the customer.

The team completed their coding milestone a week late (and worked a lot of overtime). 
Finding the root cause for a failing end-to-end test is painful and can take a long time. 
Partner failures and lab failures ruined the test results on multiple days. 
Many smaller bugs were hidden behind bigger bugs. 
End-to-end tests were flaky at times. 
Developers had to wait until the following day to know if a fix worked or not.