I've noticed that the LLBLGen generated code creates an entry in the app.config file for the connection string that includes "Packet Size=4096" at the end. Is there any reason why this setting should be used instead of the default 8K?

That's the optimum. Please check the following links:

http://msdn2.microsoft.com/en-us/library/ms130822.aspx

http://support.microsoft.com/?kbid=903002

Actually, I picked the default as it's also produced by vs.net . As it's a connection string available in your own app.config, you can of course change it as you see fit.