You can find the download instructions here. Feel free to download the CTP, use it and give us any useful feedback you may have. Tell us what you like, what you wish we had implemented, and what areas you think we can improve upon. Please send your feedback to us via our discussion forum or our product feedback center on the Microsoft Expression Web site. You can also respond to me and I will communicate your feedback to the folks in our team.
The purpose of the CTP is to get a feel from our customers out there and incorporate their feedback into the next version of the CTP. The sooner we get your feedback, the better.
Also, you can try out the samples that are posted in my blog on the March CTP build.
Please read the Readme file for the March CTP which contains known issues and workarounds.
Now, go ahead and have fun with the tool!