Photosynth, the online service which creates a 3D "synth" you can explore out of 2D photographs, has moved over to Silverlight for its default viewer. Formally you required a Direct3D based browser plugin to make use of it, and as such this opens up Photosynth to a much larger audience.
The biggest advantage from using Silverlight is obviously embedding it in other websites, if I embedded a Photosynth with the D3D viewer - about two people would have it installed, however most people visiting this blog do have Silverlight installed. Heck let's embed one I did earlier today:
It does have its downsides, such as lower performance, but once Silverlight 3 is released and we get some hardware acceleration the difference should level out. At the moment you can still use the Direct3D viewer if you have it installed on the Photosynth website.
There's also a new highlights feature. Which enables the synth author to select specific images of interest, this is also welcome as you can get lost in a synth comprised of several hundred images quite easily. Above is my synth of Norton Sub Hamdon church updated with a some highlights to give you the idea.