I'm not a big Instagram user, but the addition of video has created some strong, and diametrically opposed, views:
This could introduce a whole new style of mobile movie making, beyond simply sharing your clips on Instagram itself. Just like the square format in still photography, this look presents a different view of the world compared to 4:3 or 16:9.
They did this to spite Vine (and Twitter, which owns Vine), not because it makes Instagram better, because it doesn’t make Instagram better, it makes it worse. Slow to load, noise I don’t want, bursts their bubble of simplicity and focus. Thankfully there’s a setting to turn off “Auto-Play Videos”; otherwise I’d abandon ship.