The latest build for the Windows 10 Insider Preview for phones is now available for download. The new build number is 10080 and is released to the Fast ring.

The update includes many improvements and adds support for new devices including the Lumia 930, Lumia Icon, Lumia 640 and 640XL. In addition, the latest build will also work on HTC One M8 for Windows. Verizon's HTC One M8 for Windows with version 8.10.15143.154 will not be getting the build yet.

The new build also brings many new features. They include new Windows Store beta, universal Office apps, Xbox, Video and Music preview apps and update camera app as well.

If you still haven't tried out Windows 10 technical preview for phone, here's how you can enroll and install - How To Install Windows 10 Technical Preview On Your Lumia Devices. Note that I don’t recommend users to install it on their primary device

If you have proceeded and are facing problems and issues with the technical preview for phone and want to roll back to Windows Phone 8.1. Follow the instruction in this page - How To Revert Windows 10 Phone Preview Back To Windows Phone 8.1

Here's what's new in Windows 10 Insider Preview Build 10080 for phone

Windows Store Beta for Phones- The build brings the first look at new Windows Store for Windows 10 Mobile. It has a new visual design and is built using the new Universal Windows Platform code. Both the app selection and markets where the Store Beta is available are limited in this release. Users can browse, search and download apps. Payment options include international credit card, gift cards and PayPal, carrier billing is not enabled yet. Now users can purchase movies and TV shows via the store. Purchase of music is now available in this build but will be coming soon.

Universal Office apps: Now that the Store Beta is included in this build, you can download the Word, Excel, PowerPoint and OneNote Preview apps. For more information on the Universal Office apps – read this blog post from the Office Blog.

Xbox app: It is available on Store Beta. With the Xbox app on your phone – you can access your activity feed, achievements, friends list, activity alerts, messages, watch Game DVR clips, and connect to your Xbox One.

Music Preview app: You can access your music collection and play all your music including songs from OneDrive. The new experience for Now Playing makes it easy to swipe between songs and it looks great. Microsoft has promised more improvements in future app updates including Live Tile showing what's currently playing, pinning favorites to start screen, exploring full catalog and listening to Radio with Xbox Music pass, support for kids corner, abilty to show for music in Store Beta and much more.

Video Preview app: Browse and play video files (including MKV files) on your device. You can now filter, sort and add folders to your collection. You can also browse and play movies and TV shows you purchased and rented from Xbox Video. In future update Microsoft will add the ability to download movies and TV shows for offline playback, new device management so you can manage your offline downloads on the devices, improved search results, movie reviews and cast info and many more.

New Camera app:  Make the Camera app your default camera app by going to Settings > System > Photos & Camera (or pin it to your Start screen). Note that high-end Lumia devices (1520, 1020, 930, 830, 640, and 640XL) have some features not supported by the new Camera app. For these devices, the new app will work but to get the full functionality from your device you will need to use the Lumia Camera app. Microsoft wants your feedback on the new Camera app for Windows 10 Mobile and wants you to try out  HDR (click the magic wand button), video stabilization for video and look for faces getting recognized (not identified) in the camera preview window (will help with autofocus).

Microsoft has also fixed some issues that were found in previous builds. "Tapping on an e-mail notification now launches you into that e-mail message instead of the calendar. Incoming calls should play a ringing sound now."

As the build is being released to the Fast Ring, there will be some bugs that will affect your experience. There are some migration issues after you upgrade to the new build. Here's what you might run into

• 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.

Here are the other known issues in this build-

• 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