Ok, so Microsoft removed row level security from SQL Server 2005 early in the development cycle. Pity, but looks like it was just one of those trade-offs that needed to be made.
A bunch of guys from Microsoft Consulting has produced a paper on how to implement "Row and Cell" level security in SQL Server 2005.
"Implementing Row and Cell Level Security in Classified Databases Using SQL Server 2005" http://www.microsoft.com/technet/prodtechnol/sql/2005/multisec.mspx
I like the idea of keeping it simple, yet still powerful though roles. It is a bit of work, but compared to what we have in SQL Server 2000, it is a workable and maintainable solution.
Some basic rules have to be followed, but once everyone on the development team understand them, it gets very easy. Developing with security as a base, and doing most of the DB architecture up front in still a foreign concept for most developers, even those in corporates. With the added complexity of the new features in SQL Server 2005, you can really end up in trouble if the implementation is not though through first.