Overusing "using" in .NET?

is there any kind of performance hit by having too many "using" namespace declarations (that aren't needed)?

sometimes i get sloppy and leave in some "using" statements that reference namespaces that are not used in the code. also, i tend to leave the default using's (i.e. "using System.Collections.Generic", "using System.Linq") in the code even though i don't use them in simple classes.