1. Connecting to a hidden SSID: Some people use a hidden SSID under the illusion that it provides some level of security, even though it doesn't. Windows Phone 7 originally wouldn't connect to a hidden Wi-Fi access point at all. Now it will, but there is a caveat. The manufacturer or carrier also has to ensure the phone is running an updated Wi-Fi driver. If you have Mango and still cannot connect to a hidden SSID, contact your carrier. Mango has the capability and Microsoft has done all it can on this front.
2. Threaded email conversations: This is one of those love it or hate it features and some people love it. If you fall into that camp, then do nothing. Mango enables this by default. You can easily turn it off on a per-mailbox basis though.
3. Linked inboxes: If you have to manage multiple mailboxes, you can now see them all at once. Mango keeps the databases separate, but visually it looks like one big mailbox with all of your mail. A reply is sent from the mailbox it was sent to and all preferences are kept separate, so things like how long an email is retained and signatures are on a per-mailbox basis. You can link all, some, or none of your mailboxes, depending on your preferences.
4. Better live tiles: Live tiles in Windows Phone 7 were nice but didn't always function properly, especially third-party tiles. The more you had enabled, the more likely you were to run into problems. Once you had 15, you were maxed out. Additional live tiles were static. Mango upped the limit to 30 live tiles and improved the performance of all of them. They work best when a third-party developer redoes its tile to support multitasking. So feel free to add as many inboxes, people, and weather tiles to your homescreen. Having multiple weather tiles, with apps like WeatherLive, makes traveling easier as you can see the weather conditions at all of your travel destinations at a glance.
5. Contact history: This has been greatly improved. Simply pull up a contact in the people hub, or tap on a person if they are pinned to your homescreen, and swipe to the history section. You will be able to see all of your recent interactions with them via phone, SMS, and email. Tapping on any of those will bring you to that item. You could reply to an email right there, for instance. An additional swipe to the What's New section will show you their social interactions on Twitter and Facebook, including things like @replies to you.
6. Task switching: If you are like most professionals, you are doing multiple things at once. Twitter, email, checking out an Excel document, looking for directions, etc. Now you can seamlessly move through these by pressing and holding the back button. A task window showing thumbnails of recent apps pops up that will allow you to go directly to any of them. This works with all apps, but the experience is faster and more likely to return you to exactly where you were if it has been rewritten to support this feature. If you have ever used or seen the app-switching cards in WebOS, then you know exactly what this looks like.
This barely scratches the surface, but it gives you a hint of some of the improvements in Mango that makes the life of a professional, especially one that travels, a bit easier.