This just came in from Toney Sisk, a writer in the Project IW team:

If you are a project manager who wants to create a project using Project Server 2007, you have two ways of connecting to it. You can connect directly using a Web browser and a URL given to you by an administrator, or you can connect through Project Professional 2007 on your desktop, which is explained explain in this video.

http://office.microsoft.com/en-us/project/HA102910371033.aspx?pid=CH100948801033