I love that it is very quick to setup, you just need 3 things- Admin access, an API key from Google Apps Marketplace (which can be easily found), and some HTML knowledge. You don't have to log in as another user or anything like this which makes life easier when testing out new features before rolling them into our apps without first taking test feedback from users! There are other tools out there but these two seem the most customizable by developers. This isn't necessarily bad though because they do what we want so well. We were using Pivotal Tracker previously but realized people hated logging in via browser each time so wanted something more streamlined and faster. Since implementing ATSG, we've seen increased use of our apps - particularly after release dates since everyone now has instant test results upon login.