Just as a usability issue, most of the topics mentioned in the "What's New" documents have a link to further information. The GROUPING SETS item under "What's New in CTP 1" at /s10de_0evalplan/html/8f625d5a-763c-4440-97b8-4b823a6e2439.htm should contain a link to the GROUPING SETS topic. Of course, the GROUPING SETS entry in the index currently points to /s10de_6tsql/html/c1050658-b19f-42ee-9a05-ecd6a73b896c.htm which is actually the topic GROUPING_ID (Transact-SQL).

I realize that "What's New in CTP 1" will go away but I assume these groups of topics will be combined into a grander "What's New in SQL Server 2008" section distributed with RTM Books Online.