[via Jon's Radio]
I suppose if 6 years is a while, then yes. Back then XSLT wasn't readily available but even the venerable IE4 was a powerful beast to do things with, such as ALF. Jon goes on to comment:
... but now Google has legitimized them ... My guess is that we'll see an explosion of pent-up creativity as more Web developers discover, and begin to exploit, the full power available to them.
Since it's something I've believed in all the years then I hope so, but I still reckon you need to break out of the browser and have have control over the windows as you can with Zeepe.