This is of course not true. Although a carefully hidden feature, it is very easy to enable it. After that you are not required to build and run your Silverlight application to see a preview of it.
Here is what VS 2008 looks like after you installed the Silverlight 3 tools:
![a picture in a bl0g](http://umbraworks.net/bl0g/vs2008_silverlight_nodesigner.jpg)
I would like to call your attention to the very bottom, where you can see double lines. I drew a red rectangle there in the image above. When you move your mouse very carefully there, it will switch into a splitter cursor. Sometimes it will just flash for a second, but move your mouse very gently, and you can find it there (it is probably only 1 pixel thick, so accelerated mouse might have problem finding it).
Now click and drag, and voila!
![a picture in a bl0g](http://umbraworks.net/bl0g/vs2008_silverlight_nodesignerloaded.jpg)
Now simply click resume loading the designer. And you now have your full XAML preview only designer. You can zoom in and out and check out how your XAML page/control will look like.
While you cannot use it to actually drag and drop controls, it still saves a lot of time when you do not need to compile and run to see the end results.
![a picture in a bl0g](http://umbraworks.net/bl0g/vs2008_silverlight_visibledesigner.jpg)