UPDATE: Now that silverlight 2 beta has arrived, I'm feeling a lot better. 

It seems that things are moving faster than I've expected. There has only been an alpha release of Silverlight 1.1, but since it is becoming bigger and bigger the branding people at Microsoft have decided that it is such a huge step forward they've rebranded it to SilverLight 2.0: 

...We now have a extensible control framework, two-way data binding, templates, styles, all the standard controls (TextBox, ScrollBar, CheckBox, RadioButton etc.), multiple layout containers (Grid, StackPanel, Canvas). In short, if you're familiar with WPF today, you'll be right at home with Silverlight 2.0.

With regards to the Rich Internet Application stuff, here's an interesting quote from the article on Tim Sneath's blog:

Moving forward, if you want to build a rich Internet application, Silverlight should absolutely be at the top of your list for consideration. No other platform will offer such a rich UI framework, and all the data templates and styling capabilities, coupled with the power of the .NET Framework and base class libraries, along with an easy migration path to a full unrestricted Windows desktop solution.

I'd better get up to speed with WPF...