One of the things that held up the release was we spent Monday trying to figure out why the communication between the source control mid-tier and client was terrible. Downloads were taking forever, as were large web service responses. We thought it might be a bug in our code or a bug in the framework. At the end of a long day, it turned out that the duplex settings for the network cards in the test machines were wrong, causing dropped packets. Evidently the image used to set up the machines was wrong.
I've written about some of the July CTP changes before. Try it out!