Hot on the heels of its tablet Big Reveal, Microsoft has previewed a major upgrade to its smartphone software.

There is good news, and bad news.

First, the bad news. It doesn't look like any handset running Windows Phone 7 today will be upgradeable to Windows Phone 8.

"All signs point to no," Auckland-based, Windows-focused developer Ben Gracewood told NBR ONLINE this morning. [UPDATE: Microsoft confirms this is the case.]

"If I'd bought a Nokia Lumia 800," I'd be pretty mad right now, quipped NBR ONLINE's resident Windows Phone fanboy, Caleb Allison (who sports a handset running a more ancient version of the OS).

 Caleb says he won't buy another phone until after Windows Phone 8 is released later this year. I'm figuring others will think the same way. That's bad news for Nokia, Microsoft's only major phone partner at this point (as a consolation prize, those with Windows Phone 7.5 software on their smartphone today should be able to upgrade to Windows Phone 7.8, which will share a number of Windows Phone 8's interface upgrades).

The good news, for developers like Mr Gracewood, and customers, is that Windows Phone 8 will share a lot of code with Windows 8 (also on the way).

This makes it easy for the likes of Mr Gracewood's company, Marker Metro, to create apps that will run on a Windows 8 Phone, or Windows 8 Surface Pro tablet or Windows 8 PC - an attractive proposition for developers, and one that should help Microsoft expand its pool of apps.

To me, one of Windows Phone 8's sexiest features is that it will treat a Skype call like just another phone call (Skype being a recent Microsoft acquisition). 

That probably won't impress phone companies like Telecom, Vodafone and 2degrees, who aren't great fans of internet calling, and who have so far done little by way of co-promotion for Windows Phone devices.

Still, useful and progressive stuff - and it's the sort of thing that could see it make real strides in its efforts to chase down Apple and Android's big, big lead.

Those familar with the current version of Windows Phone will appreciate some of the interface tricks new Windows Phone 8, too, such as the ability to resize tiles.

Windows Phone 8 also adds:

• support for 720p (high definition screens)
• support for NFC (near field communication, which can be used for contact-less payments), plus associated e-wallet software
• NFC will also be deployed for swapping files by bumping two phones together (one of the Samsung Galaxy S 3's tricks over in the Android camp)
• built-in Nokia Maps 
• support for dual and quad core processors
• support for MicroSD cards
• better tools for business including device encryption, remote management and shared hubs for staff or employees

Handset partners
No specific timetable was given for Windows Phone 8, but Huawei has said it will release a Windows Phone 8-based handset by the end of this year.

Nokia is also on board, of course (though it did muddy the waters earlier this week by releasing a new smartphone, the 808, running on Symbian).

And so are Samsung and HTC - although it remains to be seen how much of a push they'll give Windows Phone 8 models. Both have Windows Phone 7.5 models on the market, but they're lost amid the pair's heavy Android assault.