In the past mobile versions of Microsoft apps were always a compromise, but increasingly desktop rendering tools are also being used on mobile operating systems
In the above video we have a comparison of Powerpoint mobile in Windows Phone 7.5 Mango with the latest version of Office.
The slideshow is not incredibly complex, but does include a number of transitions and effects which I frankly expected would fail on mobile, and clearly fidelity to the original is pretty good.
What the OS really needs to make this useful is of course a form of TV out, and we can only hope the rumoured HDMI-out on the HTC Titan is in fact real and functional, making this useful for a bit more than just rehearing presentations.