Nokia's Lumia 800 leaves a solid first impression. I had a few minutes to play with it when the phone was first unveiled, and I came away from that thinking that this was finally it. The Nokia Lumia 800 was Windows Phone 7's killer smartphone. That prototype Lumia 800 felt great in the hand, ran the latest Windows Phone 7.5 Mango and was lightning fast, even without any fancy dual-core processors. The Lumia 800 felt like the best Windows Phone 7 device to ever arrive. I finally had a chance to use it for a few weeks (this review would have arrived sooner if not for a battery charging-related software update that couldn't be done manually and Wi-Fi issues that required us to get a replacement) and I'm sadder than I was that brisk October morning. Read on to find out what happened.