TagItBest is designed to streamline the application of tags to your images, allowing you to quickly add them to any image on your account, but there are issues with the interface and setup. If you look past these initial issues, the app is fairly well polished, easy to use, and well integrated with your Instagram account, which are all good things for those in need of a more powerful tagging application.
After downloading the app, you'll need to sign up for a TagItBest account. It requires integration with Instagram, so you'll first log in with Instagram and then create a TagItBest account. With details like your birth date required, it is a bit excessive, but there are no requirements for what you enter in these slots, so privacy doesn't necessarily need to become an issue. After setup, the app runs much more smoothly. While the interface is still fairly rudimentary as this is a relatively new app, it works well, allowing you to load up and tag your images on the fly from your photo album or from the camera app. Each image can be cropped, tagged, and then uploaded onto Instagram, directly from the app--a nice touch.
TagItBest is a good idea but in need of some polish. From streamlining the setup process to ensuring the interface is more graphically attractive, there is work to be done here. But with that said, the core functionality of searching for keywords and tagging your images is very finely executed and adds a lot of depth to the app. This is a great tool that will provide a useful service to many Instagram users.