Question: I'm looking mainly at things like new SQL syntax, new kinds of locking, new capabilities etc. Not so much in the surrounding services like data warehousing and reports...

Answer: 
Did you check the whitepaper on the website? 
 [SQL Server 2008 Overview.](http://www.microsoft.com/sqlserver/2008/en/us/overview.aspx) 

I cannot recall off the top of my head, but it atleast has a nice database to object linking functionality. They have geospatial types too, if you need to use those.
Page compressiong sounds really nice to me. Haven't used it yet, though.

<http://sqlblog.com/blogs/linchi_shea/archive/2008/05/11/sql-server-2008-page-compression-compression-ratios-from-real-world-databases.aspx>