To me, the idea of running applications in the "cloud" on JavaScript and HTML is the total opposite of a new BeOS. BeOS is supposed to be lightweight and highly responsive. The Web is not. That doesn't mean that ChromeOS won't have its uses, but any other modern OS will get you closer to BeOS than this.
Not really true. I think Gears is a clear indicator of how Google sees the post-HTML5 world. Given that I think one of the driving ideas behind a ChromeOS is that programs and data will be cached to some extent on the desktop (a view that seems to be shared with Adobe (AIR) and Microsoft (Silverlight))
Web apps that are cached should be both light weight and responsive
Compared to BeOS, Web apps that are cached are in no way lightweight and responsive. Maybe we're defining lightweight and responsive differently. I am thinking about the real-time media capabilities of BeOS which let you drag around videos on Pentium IIs. I'm thinking about native C++ applications and a completely multithreaded system. I'm thinking about Gobe Productive and native e-mail clients. For me, lightweight runs on a Pentium Pro with 64MB RAM.
Gmail is not lightweight. Compared to Yahoo Mail or Live Mail, its design is airy, and it's well-optimized. Let's be honest: Chrome OS is only here to tap the netbooks. It's not going to revive the massive amount of old hardware that BeOS could use. YouTube isn't lightweight. Chrome's process-per-tab system isn't lightweight.
Web apps can't hope to achieve the kind of responsiveness BeOS offered, at least not for a few more years. Unless you have near-zero network latency and multithreaded JavaScript apps, you cannot possibly build responsive web apps. We will get there, sure, but it will take a while.
BTW, I know this because I use Haiku on my PC. Haiku is responsive because it has been built to be that way from the ground up :)