Vines are about to start looking a bit nicer. Over the "coming days," the Vine app will start to roll out support for higher quality videos — Vine's blog post suggests that it's bumping the resolution of each video up from 480p to 720p, which is a decent improvement. Of course, the videos still look somewhat compressed so that they can be quickly loaded on mobile, but it's an important jump nonetheless. On iOS, it sounds like new Vines will immediately start uploading in high def. As for Android, you guessed it: the feature is coming "soon."
Vine's quality comparison. Still from a 480p clip on the left, from a 720p clip on the right.