Flash is the only widely available system that gives you full control over every pixel in the browser and it does that in a pretty efficient manner.
Although, yes, something intuitively stops me, too, from getting excited about Flash. Maybe it's that it's closed/proprietary and I just don't trust today's Adobe anymore. They definitely want to be the microsoft of the web.
So there's Silverlight (well, potentially), Flash and still no decent alternative from the open-source world. No Mono/deIcaza stuff please. Thanks.