After checking out the wonders that Unity3D can bring to a browser, this is some work from the Google guys using O3D. There are some pretty neat examples on the site showing all manner of technical wizardry modifying 3D in realtime through the browser.
[shot of the Interiors Online demo using O3D running in the browser]
My take is it feels like a techy solution so far, it doesnt have the sweet Google interface class that will make it what it needs to be. The Unity engine is much more advanced from a user and interface perspective. The beach example (see vid below) from O3D is a fair way short of what Unity can do and isnt easy to move around in at all. BUT - it is WIP and I cant wait to see it after an iteration or two. Perhaps I am being a little unfair, if I hadnt seen what Unity could do, this would be very exciting :-)