Many of the OEMs are making a big push to update their flagship devices to the latest version of Android 5.1 Lollipop. HTC is the big OEM that is kind of lagging behind. Today an early build of Android 5.1 labeled "2.7.401.1" has leaked out. There are a few major changes included in this build. HTC will include the ability to tweak the color temperature of your display similar to TV displays. Another big change is the inclusion of multiuser mode. There are a few smaller features like some new UI enhancements and animations, and the addition of do not disturb mode in sound controls. This update should be rolling out to unlocked devices very soon. Of course carriers will need to add their bloat so you can expect the update a bit later if you have a carrier version.