Microsoft’s BUILD conference has kicked off in Redmond with a keynote featuring CEO Steve Ballmer, Developer evangelist Steven Guggenheimer, and Kevin Gallo from the Windows Phone team. There were also a few guest appearances, including Tony Garcia from Unity, a cross-platform games engine.

The company has a lot to talk about, with Windows 8 just launched – four million upgrades sold so far, we were told, which seems to me a middling OK but not great result – and Windows Phone 8 also fully announced for the first time.

The keynote opened with a performance by Jordan Rudess from Dream Theatre, enjoyable and somewhat relevant given that he has helped create two music apps for Windows 8, Morphwiz and Tachyon, which he talked briefly about and played on a Surface RT and Lenovo desktop.

Then Ballmer came on and gave what I can only describe as a hands-on tutorial in how to use Windows 8 apps. I found this odd but it was well received; my conclusion is that many people have not bothered to look closely at Windows 8, or have been put off by the Start menu issue, and much of what Ballmer showed was new to them. It was not to me, so I was not gripped by this section of the keynote.

I preferred the presentation from Steven Guggenheimer; most of what he presented is also covered here, and included the announcement of forthcoming Windows 8 apps from Disney, ESPN and Dropbox. The Dropbox announcement is particularly significant, since I have heard complaints about its absence from Surface RT, which is unable to run the usual desktop client for Dropbox. Another app that is on the way is from Twitter. Guggenheimer also described a new PayPal API for Windows Store apps.

I do wonder why key services like Dropbox and Twitter are only now announcing Windows 8 apps. Windows 8 has been available in preview versions since last year’s Build event, and has not changed that much as a developer platform.

Gallo introduced some of the new features in Windows Phone 8, and claimed that Microsoft has delivered the majority of developer requests in the new Phone SDK which is available from today. He emphasised the possibility of sharing code between Windows Phone 8 and Windows 8, using Visual Studio to ensure compatibility.

Garcia presented Unity for Windows Phone, which is potentially a big deal, since it is widely used. The demo of immersive gaming graphics on Windows Phone 8 was impressive.

Finally, Nokia’s Richard Kerris came on, mostly to announce a giveaway of the new 920 Windows Phone 8 device for Build attendees.

This raised a loud cheer as you would expect, though it may be significant that the free phone won an even warmer reception than the earlier announcement of a free Surface RT.

The cost of signing up for a Windows Phone developer account has been reduced to just $8.00 for the next few days; see here for more details.

Did Microsoft do enough in this keynote? Personally I would like to have seen more technical depth, and a more convincing presentation of why the company thinks these new devices have what it takes to take on Apple and Google. Still, this is all about partners, and the arrival of Dropbox and Twitter as Windows 8 apps, and Unity for Windows Phone 8, are all significant events.