I just received an email this morning that testflightapp.com will no longer be active as of 2/26/2015, and that I should be using the iTunes Connect TestFlight service inste
From Apple's beta testing site:
Internal Testers Get feedback quickly by sharing your beta builds with up to 25 members of your team who have been assigned the Technical or Admin role in iTunes Connect. Each member can test on up to 10 devices.
External Testers Once you’re ready, you can invite up to 1,000 users who are not part of your development organization to beta test an app that you intend for public release on the App Store. Apps made available to external testers require a Beta App Review and must comply with the full App Store Review Guidelines before testing can begin. A review is required for new versions of your app that contain significant changes. Up to 10 apps can be tested at a time, internally or externally.
Only external testers are subject to the app store review and guidelines. TestFlight Beta Testing