The FILESTREAM feature of SQL 2008 allows more effective storage and retrieval to BLOB data.  It accomplishes this by utilizing both SQL 2008 and the NTFS file system.  In the past, most developers stored BLOB data in the SQL Server using varbinary(max).  This has some drawbacks including:  you had a 2GB max, streaming performance was awful, and recovery from fragmentation was poor.  The FILESTREAM can hold up to the size of the NTFS volume size, streaming performance is excellent, and it can recover from fragmentation on disk nicely.

By default, if the programmer does not specify the DateTime kind, .NET WCF services will serialize and deserialize DateTime objects based on the local time zone.  What this means is that if you have a client entering information on the east coast (EST) and your server is in central time (CST), the DateTime values entered by the client will have their hour decremented by 1 when the data is deserialized at the server.

PowerCommands is a set of extensions for Visual Studio which adds functionality to the IDE.  It is the #1 downloaded/rated plug-in for Visual Studio 2008 and 2010.  So I felt a bit silly as I had never heard of it until a few days ago.  Some things always bugged me about Visual Studio (ie: having to collapse each project in a solution one at a time, not being able to close all open documents at once, not being able to open the containing folder of a document from the document window, etc).  PowerCommands has these features and many more.