This would be your best tool for creating graphics that you want to use in the animation. It creates great quality vector graphics.
I agree that presently there is a limited tool set in Design. But inspite of that, I would recommend using Design to create graphics for adding to Blend 2 animation. First of all they have great compatibility. To maintain quality you can simply paste these graphics into Blend 2 and animate. The only issue with that is it will create multiple canvases in Blend, as each element of your graphic will create XAML. That's why they seamlessly transfer - by way of XAML - to your Expression Blend project. The work around is to create good quality PNG and import into Blend 2.
There are some nice effects that can be added to the images too if you are working with images.
Here's the link to download the trial version of Experssion Design:
Check out the features of Expression Design: