If you've been using XamlPad to create small Xaml examples for your own education or for posting snippets on forums and blogs I suggest you do yourself a favor and download Kazaml.
It has the simplicity and flexibility of XamlPad but it actually has syntax hilighting, intellisense and theme / style snippets to help you out along the way. It also has the ability to have multiple Xaml files open simultaneously in tabs. I found it very convenient.
So if you're interested in learning some WPF or you're looking to just upgrade your XamlPad go check this out for sure.