Having used the new Nokia Lumia 900 for about a week I’ve got some experience with it compared to my current phone Lumia 800.
Currently Windows Phone 7.5 only supports display resolution of 480×800 pixels which means the Lumia 800 with a 3,7-inch screen has the pixels density of 252 pixels per inch (ppi). Lumia 900 has the same resolution on a 4,3-inch screen which means a smaller pixel density of 217 ppi.
I haven’t noticed any image quality issues on Lumia 900. Graphics and photos just don’t look as impressive as on phones with better displays, such as Apple iPhone 4S (3,5-inch, 640×960, 326 ppi), HTC One X (4,7-inch, 720×1280, 312 ppi) or Samsung Galaxy S3 (4,8-inch, 720×1280, 306 ppi).
Windows Phone 8 is expected to support higher resolution screens, but until that device vendors are stuck with the current resolution.
However, there’s actually one benefit with the smaller pixel density. The virtual touch screen keyboard on Lumia 900 has a bit larger letters than on Lumia 800 which makes it easier to write messages. This can be very helpful for people with a bad eyesight or less accurate fingers using the touch screen.
The most important technical advantage of Lumia 900 compared to Lumia 800 is the support for DC-HSDPA, the latest evolution of 3,5G networks. It offers theoritical download speeds up to over 40 megabits per second (compared to about 20 megabits of Lumia 800), Mobile operators in Finland already support this in lots of cities, but the coverage seems to be quite small. You usually also need a new mobile data plan to take advantage of the higher speeds.
Lumia 900 also has a front-facing camera for video calls, but I haven’t had any use for that yet.
Battery life has been a big problem for Lumia 800, even though the latest firmware update fixed this significantly. I’m still not sure if Lumia 900 is any better. It has a more powerful battery, but the larger display also consumes more power. I have tried a total of around five Windows Phone devices, and of these Samsung Omnia W (with a 3,7-inch screen) has offered the best battery life so far.
I’ve found internet connection sharing (or tethering) to be useful new feature compared to Lumia 800. It was a big help this week when travelling, and internet access using the WLAN connection in my hotel room suddenly stopped working. In less than a minute I had activated the tethering on Lumia 900. With a mobile subscription supporting DC-HSDPA, I could reach peak download rates of about 17 megabits per second and latency of around 20 milliseconds in Elisa’s network Helsinki using the speedtest.net test site. I think that’s quite impressive for tethering.
In the end, internet connection sharing is not a reason to upgrade to Lumia 900, as it’s a standard feature on Windows Phone, but Nokia hasn’t had a driver for it before. That’s why they’re shipping it first on Lumia 610 and 900. Nokia has announced it will become available as an update for Lumia 710 and 800 too.
Lumia 800 still remains to be my favourite Lumia model. I also feel Lumia 900 is a bit too heavy and large to carry around everywhere. If I watched lots of videos and my mobile subscription (by my employer) supported DC-HSDPA, I guess Lumia 900 would be my preferred choice.