Microsoft had initially planned to release the Lumia Denim update before the beginning of 2015. However, the tech giant has just started to roll out the update to a limited number of mobile devices found in certain markets. The roll out shall continue in waves and shall be done by device.

Some of the devices which are confirmed to receive the update include the newly announced Lumia 435 and 532 models which are both priced below $100. Older devices should expect to have the update soon.

"The Lumia Denim update has started rolling out to a limited number of devices in selected markets and will continue arriving in waves by device," said Microsoft in a blog post. "A wider rollout of Lumia Denim to all Lumia smartphones running Windows Phone 8.1 is expected to begin this month following partner testing and approvals."

Lumia Denim features a number of highlights that aim to enhance the user's overall experience. One significant highlight is Cortana, Siri's counterpart. Cortana is said to be made available to eligible devices of users coming from China, the U.S. and the U.K. in beta versions. Users from Spain, Germany, Italy, France, India, Canada and Australia shall receive the feature in alpha mode. In the update, users can take advantage of the voice activation feature found in Cortana which allows them to wake their device from being idle at a time by simply uttering "Hey Cortana."

Another feature that users should watch out for is the Live Folders which allows them to organize their apps into folders. This can come in handy particularly when they access certain apps regularly. It also features a newly -updated Glance Screen which displays fitness and other activity from the health niche as specified in MSN's Health and Fitness app.

Other features brought by the Lumia Denim include an improved Internet Explorer and Consumer VPN for Lumia 1020 users. The latter provides improved safety and security for the device when it is connected to WiFi networks in public and unprotected areas.

Some devices such as the Lumia Icon, Lumia 830, Lumia 930 and Lumia 1520 are getting an upgraded Lumia Camera brought by the Lumia Denim update. Microsoft says that the upgraded camera app promises to deliver "images that are of the highest quality at the fastest speed with only milliseconds between shots."

However, Lumia 1020 owners will not get the newly upgraded Lumia Camera in their devices. Microsoft explains that the "exact contents coming with Lumia Denim vary depending on the device model."