In some cases, users may have to request a key if they were already in the queue for the beta. In that case you may have to go to the web site and click the “Request a Key” option and you will be granted access to the beta.
We have been looking at the beta for a bit now and we can tell you that it simply has a lot of abilities and can help anyone create something with Spark. To create with Spark is the entire point and it will be interesting to see what people are able to develop using it.