If technology is easier to understand and implement and at the same time complex enough to handle heavy tasks it increases it chances of becoming popular. Languages like "C", "C++" are the examples of it. ".Net 2.0" made programming even easier and gave us more control to develop applications which are more complex but easier to design.
.Net 3.0 makes designing of applications even simpler, XAML is the coolest thing to happen in recent times. I wonder its so simple to make a major change in application just by adding a group of simple tags. Microsoft Expression Blend is the tool used to design applications in .NET 3.0. As you design the interface, the XAML is written by the software, though you can also write XAML to make changes.
XAML Code for making a simple button is very simple:

<Button Width="100" Height="40" Content="Button"/>
What makes it even cooler is that we can add subtags to this easily, to enhance the control for eg. in the code above if we add subtags <Button.BitmapEffect> as shown in code below we can use the <DropShadowBitmapEffect> to give shadow to the button
<Button Width="100" Height="40" Content="Button">
<Button.BitmapEffect>
<DropShadowBitmapEffect Direction="315" ShadowDepth="2" Softness="1"/>
</Button.BitmapEffect>
</Button>
.Net 3.0 ships with a feature in the built in dictionary wich provides spell-checking on a textbox or RichTextBox control. Also it allows a context menu for the suggestions of alternatives for the replacement of the misspelt word. Following code shows us how. When the propery "SpellCheck.IsEnabled" is set to True TextBox will mark all misspled words with wavy red line like Mircosoft word.

<StackPanel Margin="20">
<TextBlock>TextBox</TextBlock>
<TextBox SpellCheck.IsEnabled="True">
Speling is wrong and underlined with wavy line
</TextBox>
</StackPanel>
When you execute this code you will see Textbox with red way line under "speling" which is spelled incorrectly. Right click on it to see the alternatives.
To learn about more cool features and power of XAML and Microsoft Expression Blend watch the screencast Revolutions which is hosted by Dax and Andy.
