You get a full-size keyboard that lacks two critical keys: Page Up and Page Down. That makes it hard to scroll through text-oriented applications, and I found no shortcuts to simulate these essential keys. The keyboard is very much modeled after an Apple keyboard, and Apple dropped Page Up and Page Down years ago from its laptops -- an Apple interface decision that should not be copied. You can scroll using the trackpad with the two-finger gesture common on other operating systems, but it's not the same as paging up and down.
There's also no Caps Lock key (a Search key takes its place); Google said the goal was to eliminate "yelling" in website comments. That's a charmingly naive rationale for people who must only spend time on the Web. Getting rid of it to control silly Web commenters is dumb social engneering on Google's part. (What's next: getting rid of the question-mark symbol to prevent dumb questions?) I can live without a Caps Lock key, but it is actually useful in writing; fortunately, Chrome OS has a setting to make the Search key act as a Caps Lock key instead.
The Chromebook also gets rid of the function keys that PCs borrowed from mainframes 30 years ago. I won't miss them, although I'll be curious how remote control applications such as the promised Citrix Receiver for Chrome OS will deal with Windows Server apps that use them. Instead, there's a row of keys that are heavily inspired by Apple MacBook keyboards, with keys for brightness, audio volume, full-screen mode, and tab switching (which doesn't work yet), plus Web-oriented keys for Back, Forward, and Refresh. No Home key, though. I also can't find a way to enter accented letters or special symbols such as the euro symbol.
There's not much else on a Chromebook. The protototype has one USB port to support mice, keyboards, and (not yet implemented) storage. There's also an SD card slot, an audio jack, and a VGA video port. Nothing happened when I inserted an SD card or USB thumb drive, and attaching an external USB drive just caused it to click repeatedly. At this point, the only files accessible are those stored in the Downloads "folder" (a browser tab like everything else) after being downloaded from the Web. (Google's help page suggests the storage device capabilities aren't yet implemented.)
In any event, it's clear that Chromebooks will be simple devices. I'd add a second USB port, but there's no reason to lard up Chromebooks with all the ports that most laptops have these days. The support for Bluetooth devices such as keyboards also helps reduce the need for dedicated ports.
Looking forward to the next beta roundHardware, of course, is not what the Chrome OS is all about. Frankly, the Chromebook device is nothing more than a package to contain Google Docs and other Web services from Google and others. It's a Google Docs-plus-Web appliance.