For a phone that’s only recently been launched the Nokia Lumia 710 for T-Mobile is already turning out to be a best-seller.

No doubt helped by T-Mobile’s huge advertising spend on the new Nokia 4G phone, the Lumia 710 is currently boasting a 5-star rating based on over 40 user reviews submitted to the official T-Mobile online store.

That’s great news for the new generation of Windows 4G phones as well as for Nokia who have been making noises for a while about wanting to become more of a force in the marketplace.

So what’s the fuss about?

The Lumia 710 is an affordable Windows Phone 7 smartphone (currently $99 on Amazon) that comes equipped with full T-Mobile 4G network capability (with 3G backup) and a comfortable 3.7-inch touchscreen.

Although you couldn’t describe the Nokia Lumia 710 as a high-end phone, it does come with a set of very respectable specs for a phone at this price point. As well as the latest version of Windows Phone 7.5 (Mango), which is vastly improved over previous versions of the OS, the Lumia has a fast 1.4GHz processor, 8GB of pre-installed memory, full Wi-Fi networking and Bluetooth as well as a 5-megapixel camera – which performs well even in challenging, low-light scenes and also has HD 720p video capture.

In terms of mobile apps and entertainment, this Nokia phone is pretty comprehensive. It comes pre-loaded with T-Mobile TV with instant mobile access to on-demand HDTV from networks like ABC News NOW, FOX Sports, PBS Kids and Azteca America.

With a premuim upgrade you can also enjoy a number of other channels including ESPN Mobile TV, Disney Channel, CNBC, En Español, Life & Style, and Crackle Movies.

Mobile web surfing is fast, safe and fun with Internet Explorer Mobile, Bing Search (with voice commands), and Local Scout for truly localized and relevant search results based on your current location.

Talk and standby time are pretty good at 7 hours and 384 hours or 16 days respectively.

All in all, the new Nokia Lumia 710 is an affordable 4G phone with enough new and improved Windows mobile features like conversation threads and text messaging by voice, where you can have incoming texts read to you and reply via speech, to have earned a place on your buying shortlist.