As an example of some of the enhancements, look at the application list. One of the biggest complaints of heavy users of the platform is the list of installed applications because there is no way to organize it. It is just one big long list in alphabetical order of installed apps. Mango doesn't make a major change to it, but it is tweaked to make finding things faster than having to scroll through several screens. Once your list of installed apps grows to a certain number (I've not seen exactly what that number is) a letter in a box will show up before each alphabetical grouping. "A" for apps beginning with A, "B" for those starting with B, and so on. Tap any one of those letters and all the letters show up on the screen. Tap the letter you want and you are whisked to that section. So, if you want to go to Settings quickly, just tap the "A" at the beginning of the list to bring up the alphabet and tap the S icon.
Another way to find your app is to hit the search icon next to the app list. That is another change to the OS. The hardware search button now only launches a Bing search. All other searches will happen within the app you are in. I am not sure if that is a good change or a bad one, but apparently having the search button do different things confused enough users that Microsoft decided to make the button work in a consistent way.
As I said, there are dozens of other enhancements but most of them appear to be minor, not major overhauls of any particular area of the platform. These will make current owners happy, but Microsoft has to do at least two things to ensure it is successful.
-- The update must be free to existing owners. There is nothing out there to suggest it won't be, but given that Microsoft charged for previous major updates with Windows Mobile, it bears mentioning. Apple made paying for OS upgrades a thing of the past with the iPhone. So far, it has given away updates that let people upgrade not one but two full versions on old hardware. Microsoft can do nothing less.
-- The rollout must be smooth and fast. The NoDo update from earlier this year brought copy and paste and a lot of frustration. A few phones got the update rather quickly and others to this day still don't have it. Hopefully Microsoft has learned a lesson here and will be able to convince the manufacturers and carriers to take future updates seriously, including Mango.
If you want to see what else Mango has to offer, check out this thorough article at PocketNow. It has over 30 minutes of video and over 20 images.