Looking at HTC’s Touch Diamond handset, you’d think it was cutting edge. Touch FLO 3D interface? Check. 7.2Mbps HSDPA? Check. But as we said in our hands on piece – there’s one problem, and it’s nothing to do with HTC itself. Nope, it’s that pesky Windows OS it runs on.

Microsoft knows that Windows Mobile is not up to scratch. It made that clear during its consumer pitching at February’s Mobile World Congress in Barcelona. We expect Windows Mobile 7 and 8 to seriously challenge Apple and Nokia on interface usability.

After all, Windows Mobile still makes a mobile work like a PC. And that, as we’ve seen with the iPhone, is not the way a mobile should work.

Things will change. The fact SonyEricsson has also jumped onto the Windows Mobile bandwagon with its forthcoming Experia X1 suggests that big things are ahead for the platform, even if looking up an email is currently still equivalent to wading in treacle.

However, it must be slightly annoying for HTC that it continues to have to develop atop Windows Mobile to make its handsets anywhere near usable and, in the case of the Diamond, at all appealing to consumers. And that despite the Touch Diamond deploying the latest 6.1 version of the OS.

It must also be slightly depressing for Microsoft’s Mobile bods who constantly see their OS tinkered with in an effort to make it more usable. But not as half as annoying as Windows Mobile is to use…