Tip For Silverlight 2.0 Beta 1
So I downloaded the new Silverlight 2.0 goodies and have played around with them a little. If you're using the Blend 2.5 preview, here's a tip. When you create a TextBlock it creates a TextBlock then puts the text in a Run element inside it. Afterwards, if you change the font size it changes it on the TextBlock and not the Run, and the changes don't affect the actual text. To fix this annoying bug, take the Text property of the Run and put it into the parent TextBlock element and delete the Run. After that you should be good to go.
But I guess this is what we get for using CTP's :)