Nokia's partnership with Microsoft has been around for a while now, and the Lumia Windows Phone 8 headsets are the latest iteration of that partnership. With all its eggs in the Windows Phone basket, so to speak, Nokia aims to deliver a better Windows Phone experience than other manufacturers.
The Lumia 620 is the second WP8 device we've run into that features 512 MB of RAM, and like the HTC Windows Phone 8S, it's adequately able to handle most things you throw at it in what might otherwise be considered a low memory footprint. In fact, the Lumia features largely an identical specs sheet to its HTC brethren, that most advantages it will have over the 8S will be based on a superior WP8 experience.
The lockscreen features the same customizations and we're used to from the new WP8 Lumia line. It displays missed events and messages, music controls, and various Live Apps which let apps display various notifications and images. The background image can be rotated via the Bing lockscreen, and you can also let your album art become the lockscreen image whenever you're playing music.
The Modern UI features the same vertical grid of Live tiles that can be reordered whichever way you like. Almost anything can be pinned to the homescreen - apps, contacts, web pages and more. In Windows Phone 8, they're also resizable.
There's also iOS-like multitasking available, where suspended apps can be taken over by the OS, or run in the background as needed by the application. To access the multi-tasking interface, simple hold down the back button, but there is no option to "kill" an app. You have to select it an hit the back button to close it.
There's also a Siri and Google Now-like voice assistant called Microsofot TellMe, where you can dictate various commands and have the 620 carry them out. TellMe is access by holding down the Windows key.