One of the most interesting features of Instagram Plus is the ability to zoom in on any photo simply by double-tapping. You can zoom in more or move around the photo by sliding your finger across the screen. You can also download any photo or share the URL by simply selecting the option.
Instagram Plus also has some surprises in its settings. The most interesting one is probably the most simple: you can turn on the sound of the videos by default. That way, as soon as you see a video, it will start playing with sound.
Instagram Plus is an interesting alternative client which offers more features than the official Instagram app. It also seems pretty stable, so it's a viable alternative for any regular user of this popular social network.