WMExperts got their hands on HTC Touch diamond and did a full video review and large photos gallery.
I'd like to offer my professional opinion after carefully watching thru the video.
First of all I'd like to bring my opinion in short version - HTC made so far the "iPhoniest" design yet, easily beats the LG Instinct, but I don't quite feel it actually beats iPhone 3G .... yet
The new Interface - TouchFLO 3D skin is in fact working pretty decent and nice , as long as you stay in the skin skin limits, slightly to left or right and you are greeted with same old ugly Windows Mobile 6.1 interface, which is pretty annoying to use with just fingers.
So - Interface - 5 points for stealing most of iPhone interface ideas, -2 points to fail make it iPhone smooth and intuitive, -5 points for fail to make it fast and -10 for having to use Windows Mobile native applications , like email - I don't blame HTC on that, Windows Mobile 6 wasn't built to controlled by touch.
Interface still looks and feels in beta - It feels unpolished in places - like some gestures would feel unnatural and some controls way to sensitive to easily use.
Btw: A little known fact: did you knew Windows Mobile 6.1 is based on Windows CE 5.0 Core OS which was released on July 2004! So regardless of HTC's best intentions you can teach old dog only so many new tricks.
Here I need to confess and eat my socks - I was wrong - New Opera Browser developed for Diamond is a FULL Browser with Web 2.0 support and even Mobile Flash, Something iPhone 3g may have or not... I wasn't impressed by rendering speeds or the fact it took several second for page to rotate in horizontal mode. Speaking of rotation delay feels like couple of seconds delay in rotating pics as well.
Keyboard: Or the lack of it :) , similar to iPhone, Diamond uses on screen keyboard, but instead of full layout, they went ala Blackberry Pearl with 2 letter per key.
The decision was most likely due to fact the screen size of HTC's phone is smaller ergo having full letter layout would make keys in vertical mode WAY too small.
However Imho Diamond got the worst of it - not too many people like Blackberry pearl keyboard, which takes it's toll getting used to. Plus the fact it's on-screen, no tactile response - forces you too look. Having both issues in one device - maybe not such good idea ....
My opinion on whole thing is - Great attempt, but still lots of "rough edges" needs to be polished out before it be a winner, like upcoming Windows Mobile 7 which based on Windows CE 6.0 (originally from Nov 2006, but development of 6.1 is in process) which will add Multi-Touch support and I believe is going to me Microsoft's first mobile platform designed to be touch controlled. Plus lets not forget my previous argument about headphones plug stay true..