If my old iPhone 4S is a mid-sized sedan, the device I’ve been using for the past day is more like an SUV. This thing is a beast. And I’m getting more and more comfortable with it.

Yes, it’s true: With the New Year approaching, I decided to try something new in my life. This weekend I made the switch to Windows Phone — plunking down $99 plus taxes and fees for the flagship Nokia Lumia 920.

Why am I doing this? I’ve tested Windows Phones in the past as part of our coverage but never used them for more than two weeks at a stretch, while always keeping my trusty iPhone within close reach. My goal in making the switch completely is to broaden my perspective and better understand the benefits and drawbacks of Microsoft’s mobile platform.

Plus, it’s looking like my colleague Taylor Soper will be sticking with Android, and getting the Samsung Galaxy S III. With our colleague John Cook recently upgrading to the iPhone 5, we thought it would make things more interesting around the office, and on the site, to have each of us on a competing mobile platform.

And lastly, it seemed like a logical extension of my other recent experiment, in which I convinced my wife to spend our iPad budget on a Microsoft Surface with Windows RT. That has actually turned out pretty well.

Why the Lumia 920? I was initially leaning toward the HTC 8X Windows Phone, just based on look and feel. But after polling my Twitter followers and holding both devices in the store, I decided to go with the Lumia 920. Although the Nokia device is thicker and heavier, the real issue for me was the face of the device and the screen size — would it be too big?

But the screen sizes are actually very comparable — 4.5 inches for the Lumia and 4.3 inches for the HTC 8X. Basically a wash. Nokia has developed some interesting Windows Phone apps, including maps, turn-by-turn directions and its City Lens application. The quality of the Nokia camera and the 32 GB of storage also were a draw for me.

In addition, Nokia has bet its future on Windows Phone, for better or worse, so the Lumia feels like it’s on front lines.

I had visions of getting the red one, but the AT&T store where I went was out of that color, so I went with basic black. Given the black casing and familiar Windows button, my daughter has started calling the Lumia 920 “the Surface Phone.” (No, I’ve been telling her, those won’t be out until next year.)

Good news for Microsoft: The salesman at the store was very helpful, knowledgable about Windows Phone, and enthusiastic about my decision, noting that he had the Lumia 920 and loved it. A far cry from the tepid sales pitch I’ve gotten in the past.

First surprise: No headphones in the box. Wait a second, ear buds don’t come standard with all phones? I guess Apple has spoiled me. Then again, I did only pay $99 for this device, compared to $299 for a 32GB iPhone 5. So I can live with it.

When I brought up the lack of ear buds, the salesman pointed out that the Lumia 920 did come with a handy SIM door key, in case I wanted to take the SIM card out later.

That was an odd thing to say, not only because a paper clip can generally do the job, but because it implied that I might want to switch the SIM to another device. Yes, it’s compatible with my iPhone 4S, in case I want to switch back, but that wouldn’t be true to my goals with this exercise.

At any rate, I’ve been using my new Windows Phone for the past day, and will have lots to share in the coming days and weeks, as I try to make this device work for me in my daily work and life. Stay tuned.

Follow-up: Window Phone Diary: Week 1 of an uncertain relationship