I really liked Landry too, although I missed Hammond.
I liked Vala, and enjoyed her story arc. I can see why you could find her annoying though!
I saw the extremes of her behaviour as a defence mechanism though. Always pushing people away so they wouldn't get close to her. I think she carried a lot of pain and guilt from when she was taken over by a goa'uld, and that's why I had sympathy with her.