Here's more news of Tango left a little muted by Microsoft

Here is small list, published by colleagues WPCentral through their experiences with different Windows  Phone device running Tango:

• New wallpapers – Now including those new “nature” themed wallpapers in the Tango ROM
• Faster numeric PIN response – At least on our 8112 devices (Titan II, Focus 2, Lumia 900), when we would attempt to unlock our PIN on our phone it would sometimes be very slow and not register, requiring you to re-enter the number. While minor, it was annoying. That was fixed by updating all our devices.
• Send ringtone via MMS – We can now attach and send ringtones to others via MMS. You can only send custom ringtones though and nothing that is “in ROM”. This in addition to the new "send voice note" and attach multiple images in an MMS that's found in Tango too.
• Letter indexing – On Windows Phone 7.x after a user installs 45 apps, the app list will automatically index, giving you the “letter picker” to jump to find your favorite app. The problem, albeit minor, was if you went below 45, the “letter picker” would not disappear. It was odd behavior and nothing we ever experienced but Tango evidently fixes this. 
• More reliable notifications – Many users are reporting better notifications, both Tile and Toast, with the Tango update. To be honest, we feel this has more to do with “flushing the system” than any actual optimizations, though perhaps there are a few.

Via WPCentral