Just yesterday, Microsoft revealed that they'll be officially calling Windows 10 for phones as Windows 10 Mobile. Building up that momentum, today the Windows Insider team released a brand new build which showcases quite a number of core Windows 10 experiences. The previous two builds only showed changes to the start screen and several applications but Build 10080 for phones included lots of new apps and features.

First off, in addition to supporting the existing devices from Build 10052, this new build adds support for the new Lumia 640 and Lumia 640 XL, the Lumia 930/Icon and also the HTC One M8 for Windows which is the first non-lumia to get the taste of Windows 10. On a side note, Build 10080 for phones is only currently available for users which opt for 'fast ring' updates.

• How to install Windows 10 Insider Preview on you Windows Phone
• Guide to restoring back to Windows Phone 8.1 from Windows 10 Insider Preview

Moving on to the feature set of this new build, as i mentioned earlier, Microsoft is implementing quite a number of Universal apps in this latest build and that includes the Music Preview app, Xbox app, Video Preview app and also a slew of Universal office apps. In addition to that, there is also a new camera app in this build which only includes simple features and Microsoft will soon bring the full feature set of the Lumia camera to this new camera app.

Finally, the single most significant update for this build is the new Store Beta app which includes a new visual update making it look identical to that of the Store on the desktop Windows 10 build.

Do note that as Windows 10 for the desktop will be launching in the Summer, but Windows 10 Mobile will only be launching during the fall in time for the holiday season. So, don't expect the rate for updates to speed up in the coming weeks.

Microsoft: Here are some known issues

• We’re aware of several migration issues after upgrading to this build.

• After upgrading, you may see duplicate tiles for apps like Search and Phone under All Apps.

• “Pending” may show under some apps after upgrade and those apps are unresponsive. Restarting the phone will clear the pending flag and the apps should work.

• All data and settings for apps installed on a SD card do not get migrated and you cannot launch these apps or install them again. Workaround is to uninstall then reinstall these apps.

• The old email app will still show up after upgrade in All Apps list with “Error” text displayed and cannot be removed. This app also shows up banged out on the Start screen if it was pinned previously. It can simply be unpinned to remove.

• When upgrading from Windows Phone 8.1 to this build, even if you have your cellular data connection turned on, it will get turned off during upgrade. Go to Settings > Network & wireless > Cellular and SIM to turn it back on.

• VERY IMPORTANT: there is a condition in which you may never receive MMS messages. Usually when someone sends you a MMS message and your phone’s cellular data connection is turned off, you will receive a “Get message” link in the text thread from the sender, allowing you to download the message once you turn your cellular data back on. There is a bug in which this link is not received in this case and the MMS message is completely lost. To ensure MMS messages are not lost, be sure to turn cellular data on (via Settings > Network & wireless > Cellular & SIM > Data connection). This issue will occur any time your cellular data connection is turned off in this build.

• If you are in a region where Cortana is enabled (US, China, UK, France, Italy, Germany, or Spain) and you have changed the default shipping language on your phone – please ensure that your region, language, and speech settings are restored to their default values before initiating the update. This is required in order to avoid a bug that will cause Cortana/Search to repeatedly crash.

• After upgrade, uninstalling an app may not remove it from the All Apps list. Usually restarting your device resolves this issue.

• Playback of movies and TV may fail with error 0x8004c029 in the Video Preview app. If it does, go here to learn more about how to fix it.

• After upgrading, the Twitter app may crash on launch. If you uninstall and reinstall the app, it should work.

• Auto-update for apps is not enabled in this build for apps installed via Store Beta. You will have to manually check for updates.

• After upgrading from Build 10052, the Insider Hub still does not launch. However, if you upgrade from Windows Phone 8.1 the Insider Hub should now launch.

SOURCE: WINDOWS BLOG