Experienced a very strang issue with a query after upgrading to SQL Server 2008 from 2005.  A query that took less than one second on SQL 2005 ended up taking 27 seconds on SQL Server 2008. 

Exact scenario:

Query that selects data and one of the columns in the select list belonged to a full text index.  If this column is not in the select list, the query runs in under one second.
Removing the full text index did not make a difference
Changing the data type from nvarchar(max) to nvarchar(3000) did not make a difference
adding a where filter of column != '' worked

Not sure why this happened and only in SQL 2008 but not in 2005 but if you are seeing the same issue, I hope this article helps.