WPXAP posted this hands on video of a leaked build of Windows 10 for phone (12544). More information, including details http://www.windowscentral.com/hands-windows-10-phone-build-12544-reveals-transparency-controls Original posted: http://www.wpxap.com/thread-834198-1-1.html
0:35 – Transparency controls for background images
0:57 – New accent color choices, up to 48 (previous was 21)
1:07 – New Spartan build 10061
1:27 – New Lumia Camera 5.5 including quick-launch on Lumia 1020. However, there does not appear to be support for Rich Capture (likely due to older S4 processor)
1:55 – New Windows Store Beta
2:22 – New call screening and contacts
2:55 – New Word and OneNote apps for Windows 10