Javascript Intellisense is one of the major improvements in Visual Studio 2008 Beta 2.  There is a nice project that extends the javascript intellisense experience for Silverlight 1.0 by Justin.  With this extension, developers will experience full javascript intellisense in VS 2008 while developing applications for Silverlight 1.0.

Default Javascript Intellisense in VS 2008 Beta 2

  Javascript Intellisense

Javascript Intellisense in VS 2008 Beta 2 with Justin's project

Javascript Intellisense for Silverlight

 As you can see, you get much more intellisense.  Follow up his blog for more.