Released just days ago, The "Perpetual Testing Initiative" has already resulted in the creation and publishing of over 35,000 user-created maps, collectively consumed via more than 1.3 million downloads via the Steam Workshop. WOW.
It's only been about 3 days since the DLC was released and those numbers are astronomical. I think we can conclude the Puzzle Creator has been a huge success and a game changer for user-made content.
Additionally in celebration of Workshop success a sale is under way with Portal 2 for 66% off, Elder Scrolls V: Skyrim for 33% off, and many of this year's Team Fortress 2 Workshop Items available for 50% off their regular price.