It's certainly well worth spending plenty of time looking through the sample code provided with the Apollo documentation. This will help you get started and shows you some of the tricks and techniques you'll need when working with Apollo. Once you've finished with the basic tutorials, the weather station sample shows many of the more advanced features, including coloured transparent windows and irregular window shapes.
One key feature that Apollo offers developers is cross-platform window controls. On a Windows machine, an Apollo application can look like a Windows application, or like OS X code on an Apple Macintosh. Alternatively, you can use Apollo's own chrome tools to build irregular windows – and even add transparency and alpha-blending effects. Apollo windows can mix vector and bitmap graphics, so you can experiment with your own UI. This is a similar approach to Microsoft's WPF – though here it gives you a lot more cross platform capabilities than the browser-hosted WPF/e. The alpha does have some limitations – including no support for drag-and-drop, and issues with using Flex components in multiple window applications.
There's still a lot of work to be done. Apollo's PDF support is currently missing, so we'll have to wait for future releases to see just how we'll be able to use PDF in our Apollo applications. While Flex makes an excellent host for the development platform, it's not as designer friendly as the rest of Adobe's creative tools. With a major refresh of its web development suite due next week, there's probably not much scope for Apollo development features to appear there – though there is the possibility of extensions and future updates (and, of course, a version of Flash that - hopefully - will work with ActionScript 3.0 and will also play well with Flex).
This is definitely alpha code (so perhaps you may want to look at the video demonstration of a rich eBay-branded Apollo application here).
The next few test releases are going to be interesting as Adobe adds features and controls and gets rid of some of the nastier bugs. However, by the time the code ships we should see something akin to the original promise - a new way of bringing internet experiences to the desktop.
Download the Apollo Alpha here (registration needed). ®