Aviate started out as a launcher that stood out as very different. It was purchased by Yahoo a few years back, and has since then been tied into several of Yahoo's other products like News Digest. The new v3.0 update is the most significant update yet, and it will probably upset most long-time Aviate users. Spaces have been replaced by a feature called Smart Stream and the whole UI looks much more like a regular launcher.
Smart Stream looks to be Yahoo's take on Google Now. It gives you various cards throughout the day based on your location and preferences. This is to the left of the main home screen, which is where Spaces used to be. Spaces provided distinct sets of apps, widgets, and settings based on your location and time of day. Most of that seems to be gone, though you can get to some basic info screens for places, your day, and so on by tapping up in the search bar. It doesn't really seem as useful, though.
The auto-categorized apps are still available to the right of the main screen, and the quick contact card is accessible with a swipe up. You can see the wallpaper behind the app collections now, rather than being a solid background. There are a ton of suggested wallpapers too.
The reviews of the new update are almost universally bad right now. People are not taking kindly to the addition of Smart Stream in place of Spaces, which admittedly doesn't seem particularly useful right now. If you updated and wish you hadn't, we've got old versions of Aviate on APK Mirror.