Reading all comments above I still don't understand the reason why kendo won't support Windows Phone 7.5 built-in IE browser.
It's very strange and the only thing you are causing, imho, is to developers start using other products that supports this devices.

Re-analyse this requirement and think twice regarding the spread of windows phone users. 

Look also here for an example of metro style web-apps: http://blogs.msdn.com/b/interoperability/archive/2012/04/26/more-news-from-ms-open-tech-announcing-the-open-source-metro-style-theme.aspx

Mango is now fully deployed. Can we expect native elements that skin according to the OS?

I.e. a tab control on Ios would work like it does now, on WP7/8 it should give us the sliding options at the top. It would be nice to write once, have work on all platforms with a native look.

Same with all of the elements. Have it skin them all according to the device. Android users don't want to see an iOS interface and WP7 users definately don't want to see iOS.

You say in one comment that you won't support WP7 because Mango is not fully deployed. And again that you won't add support until Apollo. How can you reconcile these positions?

More importantly, how can you pretend to offer a pre-skinned, "portable" browser framework that doesn't work on a key platform? This is such a no and a damned shame for the product and a black mark against Telerik. A compromised experience is better than just a no. All I hear from your blogs are excuses, not solutions.

I do hope Kendo -Mobile- supports Windows Phone Mango 7.5 as the IE9 browser on that platform support a lot  of HTML5 and CSS: http://windowsteamblog.com/windows_phone/b/wpdev/archive/2011/09/22/ie9-mobile-developer-overview.aspx. 

If not, this is a mayor no go for us because Windows Phone is definitely taken of in the business world in the Netherlands! http://www.kpn.com/zakelijk/home.htm.
Telerik is a great Microsoft partner and I hope they will be here on WP7 too.

Are you saying IE9 isn't an HTML5 browser (Mango will include it). Also, the current version is IE7, which you support for desktop users but not mobile? Odd.