If I were to buy a smartphone today, Windows Mobile would be a desperately distant fifth* on my list of preferred operating systems. But yesterday Tim Danton and I were given our first hands-on demonstration of Windows Phone 7 (you can hear more about that on this week’s podcast), and based on what we saw, WP7 could certainly be a contender when my iPhone contract expires next year.

So here are my five reasons why Windows Phone 7 could well be a winner:

1. Live tiles

The Windows Phone 7 interface is built on the concept of “live tiles”. Instead of the tightly packed grid of icons you get with the iPhone OS, the WP7 tiles have more room to breathe and – crucially – display extra information. So instead of a bald number to remind you you’ve got two appointments today, for example, the Calendar tile on WP7 can give you details of your forthcoming meeting without having to enter the calendar app itself.

This turns the WP7 home screen into an interactive dashboard. Microsoft’s developer evangelist, Paul Foster, gave the example of a Tube app that could alert you to delays on the Victoria line, for instance, or a Facebook app that shows the most recent status update.

I do worry that the screen space consumed by these interactive tiles could prove unwieldy once you’ve got more than a dozen apps installed; you can’t view more than about eight tiles without having to start scrolling up and down the home screen. Yet tiles remain the single most convincing reason to switch to WP7 that I’ve witnessed so far.

2. Design consistency

Unlike Android and indeed previous versions of Windows Mobile, Microsoft is keeping a tight grip on the WP7 interface. Handset manufacturers or mobile networks won’t be allowed to overlay splash screens on top of the WP7 menus: a Windows Phone will look and feel like a Windows Phone, whether it’s designed by HTC, Samsung or any of the company’s other hardware partners.

That consistency’s not only good for consumers – who won’t have to learn a new interface every time they switch handsets – it’s also good for app developers, who know their software will look and work the same on every WP7 handset.

3. Microsoft-managed updates

In terms of the number of third-party handset manufacturers it has to deal with, Android is the closest thing we have to Windows Phone 7, and Android’s upgrade procedure is an unholy mess. Customers are left waiting for months for the networks to push out OS upgrades and are threatened with the withdrawal of warranties if they take matters into their own hands and install them themselves.

Microsoft has clearly taken note and has dodged this particular bullet. Like Apple, Microsoft will manage all operating system upgrades itself, meaning WP7 users won’t be left waiting for their network to pull their finger out to benefit from new features and security patches.

4. Xbox Live

One of the more intriguing features of WP7 is the integration with Xbox Live. Handset owners will be able to sign in with their Xbox Live ID, and pick up a game from they left off on their Xbox console, according to Microsoft. I stress we didn’t see this is in action, and it will surely only work with the less graphically demanding games found in the Xbox Live arcade, and not the likes of Call of Duty 4, but it’s nevertheless a unique and attractive proposition.

Microsoft is also stretching the boundaries of mobile gaming. The company has demonstrated a WP7 tower defence-style game, where users actually play in their physical location using maps grabbed from the integrated Bing Maps service.

The company is even talking about delivering rewards to gamers who participate in real-world events. Driving games could reward players with extra cars if they pass a Ferrari garage, for example. The potential for such geolocation-based games and rewards is immense – just look how popular Foursquare is – and could prove to be one of the chief attractions of WP7.

5. Microsoft’s pumped

This is the first time in years that I can remember Microsoft employees arriving at our office and talking with genuine enthusiasm about the company’s mobile platform. Compare and contrast to Windows Mobile 6.5, where everyone from Steve Ballmer downwards seemed faintly embarrassed to be associated with it.

If Microsoft’s staff believe in their own product, it will make it ten times easier to convince developers to do likewise – and mobile operating systems live or die by the quality of the apps nowadays.

The Windows Phone 7 team are giving off the same buzz and confidence we witnessed with products such as Windows 7 and Xbox 360. And when Microsoft’s in that mood, it’s a formidable competitor.

(*For those of you who care, my preferred order of mobile OSes would be Apple iOS 4, Android, Symbian, BlackBerry OS, Windows Mobile 6.5, in that order. )