The full release announcement will come in the morning, but it is indeed finally here. A tremendous amount of work has gone into this release, and we're excited to offer it up for your consumption. The more eyes on the code and functionality the better. As this first beta is about function over form, you may find areas where the UI is in need of some love (particularly the order view page). However, there are open issues addressing these and other issues, so please feel free to join in with a patch or post an issue if you find a new bug.
Demo site: http://demo.commerceguys.com/dc/
The big new features to look for are of course sales tax / VAT support and the new dynamic order total field. In the checkout form, we also have Rules powered anonymous checkout, so you can finally decide how to handle user account creation through the UI. This release also includes various API enhancements recommended by developers who are already trying Commerce out in some very challenging scenarios.
That said, the next thing to happen will be you giving Commerce a try and building those magic contributed modules based on the core systems / APIs to provide essential non-core features. There are already several payment methods supported in contrib, and we'd love to see even more before 1.0.
Please note that to run the beta, you do need the latest dev versions of all of our dependencies. To get up and running quickly, you can follow the directions in my pre-beta blog post, replacing the version of Commerce linked there with this beta. : )