Who would have thought that a Windows Phone — and one from Nokia, no less — would be one of the best alternatives to Apple’s iPhone that we’ve ever seen. And at $100, it’s a downright steal. Before Nokia announced the Lumia 900 at the Consumer Electronics Show in January, I wrote that the Lumia 800, its smaller European counterpart announced last Fall, would be a bigger deal than most think. Now it’s clear that’s even more the case with the Lumia 900, which sports a bigger screen, faster 4G LTE speeds, and the combined marketing muscle of AT&T, Nokia, and Microsoft. In many ways, the Lumia 900 is the last stand for both Windows Phone and Nokia. Microsoft needs a compelling flagship mobile device to build on its sagging market share, and Nokia needs to prove that its partnership with Microsoft can pay off with a popular device. RELATED: 20 essential Android tips and tricks If this phone flops, there’s little on the immediate horizon to save Windows Phone, and Nokia will likely shift its focus to its popular low-end devices. The good: iPhone-like polish Nokia is no stranger to creating gorgeous phones, and the Lumia 900 is no exception. The company employed the same unibody polycarbonate design it first showed off in the N9 MeeGo phone, which means it doesn’t have that cheap plastic feel of so many Android phones. It also feels totally distinct from the countless look-alike smartphones on the market — just like you can never mistake the iPhone for anything else, the Lumia 900 feels like it’s in a class of its own. The phone sports two major upgrades over the Lumia 800: a bigger 4.3-inch screen to satisfy display addicts, and LTE 4G connectivity on AT&T’s network. While Verizon has a much bigger LTE rollout by this point, I found AT&T’s 4G speeds to be comparable in New York City, with downloads clocking in between 12 and 15 megabits per second, and uploads around 3 to 5 Mbps. The Lumia 900 runs an updated version of Windows Phone Mango (7.5) that includes support for LTE. Mango was the biggest update for Windows Phone yet, and on the Lumia 900 it runs like a dream. I’ve tested a few Windows Phone handsets, and while I’ve been impressed with the platform overall, there was always a lingering disconnect between Microsoft’s polished software and the fairly unexciting hardware. Not so with the Lumia 900. Perhaps because it’s the first Windows Phone not to feel like a rejected Android handset, the Lumia 900 feels perfectly in harmony with Microsoft’s slick Metro interface. At $100, the Lumia 900 also blows away most similarly-priced smartphones. Numerous Android devices are available for $100 and under, but in my experience the cheaper you go with Android devices, the more hellish the experience. Apple’s $100 8 gigabyte iPhone 4 is the strongest competitor to the Lumia 900, but for those consumers who avoid Apple products at all costs, Nokia’s new flagship is one of the few worthwhile mid-range smartphones. The bad: Windows Phone still feels limiting Despite its great hardware and the overall slickness of Windows Phone, the platform still has some drawbacks. Windows Phone recently passed the 70,000 app milestone, but that still doesn’t compare to the hundreds of thousands of apps both iOS and Android offer. Notably, some big-name apps like Pandora still aren’t officially available on the platform. And despite the Lumia 900′s slick hardware, Windows Phone’s immaturity is hard to ignore. The OS only received multitasking support (the ability to run more than one app) last fall, and it’s still not as robust as multitasking on the iPhone or Android. This may not be a problem for most potential Windows Phone users, but for techies it’ll be a major annoyance. Not surprisingly, Microsoft continues to cater to Windows users with its mobile platform, which makes it less tempting for Mac users to adopt Windows Phone. (Then again, Microsoft has likely written Apple users off as faithful iPhone fans.) For example, Microsoft offers a small app to synchronize Windows Phones on Macs, whereas PC users get to use the robust Zune software.