The Windows Insider Program is for testing out new version of Windows both for PC's and Phone's. It's for serious Windows Phone aficionados and tech experts to test out the new software.
If you think S/MIME has something to do with trying to escape an
invisible box,you might want to stick with Windows Phone 8.1 for now.
The above quote taken from the Windows Insider website, Microsoft has strictly warned users of risks from using pre-release software. If you have only one phone and use it as a daily driver it may not be a good idea.
Now that being said, Windows 10 Mobile has some pretty cool features. I won't be able to cover them all but will mention some important ones.
- Background image for Start Screen with transparency option for tiles
- Revamped Settings apps
- New Web Browser named Edge
- More Unified experience
- Universal Windows Apps
- Revamped Store
- Actionable Notifications
- New Messaging and Phone Apps
- Better and improved design and functionality of Cortana
- Windows Hello (Bio-metric verification system)
- Continuum (Desktop like experience)
There are many more tons of new things and improvements, all cannot be mentioned. And yes with the new builds of Windows 10 Insider Preview for PC's and Phone's you can call and text from your PC using Cortana.
Note: Features like Continuum and Windows Hello require new hardware and will note be available for older Lumia Phones.
Regarding the upgrade path, almost all Lumia phone are compatible with the Windows 10 Mobile Insider Preview. So it is safe to assume all those phones will be getting the official update. Microsoft has revealed that Windows 10 Mobile will starting rolling out to phones on late December.
Regarding the current status of Windows 10 Mobile Insider Preview, the latest build released is Build 10572. People across forums have been reporting great performance improvements in almost all phones. This build has brought significantly better performance improvements than any other previously released builds.
Known issues in this build include
- Visual Voicemail sync is broken on some devices. You may need to call
your voicemail directly within the Phone app > Settings > Change more
settings for Phone > Call Voicemail.
- Opening message threads within the Messaging app will crash on dual
SIM phones if the second line's Messaging tile is removed from the
Start screen (even if only a single SIM is used). The second line's
Messaging app will also appear to be removed from the All apps list.
To work around this issue, the second line messaging tile must be
linked to the first line messaging tile by opening up the first line
in the Messaging app then go to Settings > link tiles.
- On Dual SIM devices, unpinning the second line Phone tile from the
Start screen will make the entry disappear from the All apps list.
Rebooting the phone will cause the tile and application to both
- Photos cannot be selected for sharing through third party apps like
Facebook, Facebook Messenger, Instagram Beta, WhatsApp etc.
- Some devices will get into a state where the Phone app will
continually crash upon launch. Resetting the device will recover it
from this state.
- Devices that have updated from Windows Phone 8 to Windows Phone 8.1
may lose the ability to connect to Wi-Fi on Windows 10 Mobile Insider
Preview builds or may fail to update to Windows 10 Mobile Insider
Preview builds all together. You can use the Windows Device Recovery
Tool to first update your device to Windows Phone 8.1 and then
upgrade to the latest Windows 10 Mobile Insider Preview build.