All you get is BronzeLight for now...
After asked so many questions about Silverlight (SL) lately (lot of them from the Ask The Experts booth in Tech-Ed Europe), I thought about clearing some staff about it, that I think is necessary.
For now SL is on version 1.0 (I call it BronzeLight comparing to 1.1), that is the only legit version that is out there, so if you want to develop and get on production with your product, you better learn how script your way with JavaScript and through SL 1.0.
If you look further ahead... there will be SL 1.1, and 1.2 and so on... but 1.1 is still an alpha version and you can't go public with it, so all the XAML features and "WPF like" programming is not there...YET.
Also the programming model for SL except the XAML is Webish, not WPF, it's only resemble to WPF in some manners, but it definitely have nothing to do with WPF, and WPF Web application and SL are different things.
WPF browser Application (XBAP) is the way to host WPF application in a browser and it requires an installation of FW 3.0 on the client machine.
SL on the contrary requires only ~4MB and it's a plug-in in the Browser.
So for now what can you do with all this information? first, if you want to program for desktop you are looking for WPF where you can have a full featured desktop abilities, if you want to deploy it through the Web, go to XBAP, and if you want to be cross browser and work everywhere dive into SL.
For SL, you can enjoy and play with the great things offered by 1.1, but for production go and learn 1.0 (BTW, you won't regret it, since it will be a knowledge you'll use also on the next versions, communicating in client code).
If you are new to SL you can read some great posts on that on this blog site for example : Yosi Taguri, Justin-Joseph-Angel and more...
So when "GoldLight" be available... that's a whole different question... :-)