I got a chance to play around with the new feature, and it's pretty straightforward. Once you start playing a music video, you'll see a little "GIF" button along the bottom, near the playback controls. Give that a click and you're in the GIF maker. The GIF maker defaults to where the video was when you clicked the button, but you can scrub back and forth through the entire video to find the section you want to capture.
From there, you'll get a preview of the GIF, and you can use a large bar below the GIF to refine exactly what segment you want to capture. By default, you can capture about five seconds of video to a GIF, but you can trim the beginning and end to get just exactly what segment you want.
That's all there is to it -- you can add a line of text to your creation, but that's about all there is. And sharing options are limited to Facebook and Twitter, at least for now. Vevo said it'll eventually launch more tools for exporting GIFs to other places, but right now you can't just simply download a file and post it wherever you want. That alone will probably make this a niche tool for now -- if you can't put a GIF on Tumblr, it might as well not exist. Still, this is a good first step; I'm hoping Vevo brings more sharing options and adds the GIF maker to its mobile apps soon.
Speaking of its mobile app, Vevo is adding an new "activity" feed to the web and iOS (it'll come to Android soon). This gives you a place to see exactly what your friends and artists you follow on Vevo are doing, whether it is posting a new video, building a new playlist or just liking a video. The company is trying hard to make itself into a music video social network, so having this sort of feed seems like table stakes if it wants to achieve that goal. Both the activity feed and GIF maker are rolling out today if you want to give them a shot.