Anyways, I must admit I never really thought traces of rime could f**** up the a/c performance that bad (as Maxalt describes), but from now on, this F/O will start deicing a lot more often.
Depends on what your leading edge looks like. Fixed leading edges, ala DC9-10 vs extended slats, are much more sensitive to airflow separation (sandpaper, bug splat effects} than the more common extendable slats on today's big passenger jets.
As I said earlier, follow your operating manual for the equipment that your flying, for many of the reasons stated in this thread, and forget about the ole wifs tales that you might pick up on forums.