I am suprised I don't see any reviews about Mary Lynn. So here is what I think about her.
Mary Lynn Rajskub is a great actress.
She is a great addition to the show 24 especially in the first hours of the 5th season.
But I also liked her in season 4.
I never heard of her before she started appearing on 24.
She has also been working on a new movie called firewall, I dont really know what her part is in that movie but I am sure its a good one.
Overall I think she should stay for at least another season in 24.