Solid Explorer has long been one of the most popular file managers on Android because of its slick dual-pane UI and extensive feature list. However, the UI isn't what you'd call intuitive. A big material redesign is in the works, and you can test it right now by joining the Google+ community.
Solid Explorer 2.0 looks completely different from the current build. It has all of the Lollipop animations we've come to expect, along with a proper full-height navigation menu, floating action button, and colored status bar. The default blue/orange UI can be changed to whatever you like in the settings. You even get animated thumbnails for video. That's cool, but I could see it ending up a little annoying long-term. The app looks great, but I'm not sure about the icon.
The inclusion of slide-out navigation by itself makes Solid Explorer much easier to get around in. Many of the other options that were previously scattered around the bottom toolbar are now tucked in the overflow menu as well. You can go back to the toolbar in the settings, though. The dual-pane interface is still supported in the new version too.
Want to try it? Make sure you join the community below and opt into the testing program before heading to the download link.