Despite inconsistent browser implementations of its features, HTML5 is an exciting technology for creating new and powerful browser-based applications. As I previously mentioned, these applications can even run on smartphones. If you're not convinced about developing HTML5-based smartphone apps, check out Alex Kessinger's “How to Make an HTML5 iPhone App” article.
As an additional incentive for developing your own HTML5 applications, Mozilla recently announced (at the time of writing) that it's opening an app store for selling or giving away web applications. Check out The Register's “Mozilla Preempts Google With 'Open' Web App Store Prototype” article to learn more about Mozilla's announcement.
Now that you've gained some insight into HTML5 and have learned about designing HTML5 applications, and given the fact that there's a possibility to monetize your creations, there's no reason to delay jumping into HTML5 application development. I wish you the best of luck.