It is, however, only a certain breed of developer that has the mindset and the patience to build these kinds of showcase pieces. For most of us, the idea of recreating even basic Flash feats -- such as splash screens and banner ads -- in CSS3 is a bit daunting. The future is looking bright, though: Sencha has announced a new tool to take the pain out of complex CSS3 animations.
Sencha Animator is currently available as a Developer Preview running on the Mac, Windows or Linux. It's buggy as heck, but showcases an intelligent interface with timeline-based animations across all of the available properties. It's functional enough to really get into, but there's enough missing (or broken) to keep you wishing for the next update. Nonetheless, it's very exciting; the tech of the future isn't looking like a step backward anymore1.
The app will come in two editions, Standard and Ad Builder. The current developer preview is of the Standard Edition, which apparently has all the bells and whistles, it just lacks the license to use it for ad creation. Interested ad agencies will have to contact Sencha directly to talk licensing. As far as pricing on the standard edition, Sencha says only that they're "pricing standard edition like a traditional design tool: on a per user basis in the low hundreds of dollars."
You need a Sencha Forum membership to use the preview, but it's free to try after you activate your account. If you're curious about the tools that are going to shape the web of tomorrow, you can check out the demos and give it a try yourself.
1I'm choosing not to use this post as a platform to debate the merits of Flash. The fact is that Flash makes it relatively simple to create rich content for platforms that support it, and at the moment HTML5/CSS3 lack the feature set and tools that Adobe/Macromedia have developed over the last decade. I'll leave it at that.