Its amazing to me that they are still having issues with this.. being able to use your phone for normal/light tasks shouldn't warm up the device... this is no bueno. Whenever the battery heats up, it means that its discharging at a fast rate, which isn't good considering that you are only using your GPS for example.
Windows NT is great for desktop/server, but they still have work to do on the mobile side.. its has come a long way, but its still far away from a pure mobile oriented core like EKA2 for example. Hopefully they will manage to figure it out soon..
I am impressed with the work Apple has done on iOS to be honest, especially considering that its based on Unix (Darwin) kernel.. they've come a long way, and still look what I pulled out of an iPhone 5 a few days ago:
It was melted/stuck onto the panel, so they still have work to do, but overall I would say Darwin > Windows NT when it comes to mobile (limited resources), etc.
But both are inferior to EKA2 which was developed with all that in mind from the ground up.