Or is this simply the same functionality already available on desktop browsers being brought to mobile? I got the impression it was a new level of detail.

I'm not sure if this feature can realistically be brought to desktop at this point.

We're talking about a whole lot of 3D rendering, many polygons, and a whole crapload of textures. Easy pickings for a smartphone native app, where just about every major phone on the market has obscene amounts of hardware acceleration under the hood.

Not so easy for desktops - whose graphical performance is often nearly non-existent. Not to mention you take another huge performance hit from WebGL... which also has poor penetration. So not only would most users be unable to use your newfangled 3D maps, many of the ones that can, will have an unusably slow experience.

This is one of those places where native apps really shine.

Most desktops, even those with crappy Intel GPUs have superior GPU performance to the best mobile devices. WebGL has poor penetration, but you really don't take much performance hit as long as you don't need to process data in JS, but then again, a modern i5 or i7 is much faster than an ARM on a mobile device, so what you loose in JS performance, you gain in CPU performance.

Current JS and WebGL performance is well within the range needed to make this work. MapsGL is already rendering a quite large workload, in fact, my intuition is that the 2D rendering, especially with rasterizing label text all over the place, is likely more expensive than navigating an octree and rendering a mesh.

Desktops have inferior 3d rendering capabilities compared to smart phones? Since when? Any desktop bought in the last 5 years will have an integrated or dedicated graphics chip that can at least match smartphone capabilities in this area. This can be demonstrated easily by using your desktop to browse Nokia's 3d map demo, which is equivalent to what Google is doing here. Whether WebGL is fast enough to do this on it's own is open to debate, but there isn't anything to indicate these 3d maps are particularly demanding for desktops.

Parent should be captured for posterity:

2000 - "Run this on a phone? You're crazy" 2012 - "Run this on a desktop? Insane!"

Hopefully they can at least get it on Google Earth soon.