In sight reading, sounding parts out by ear, and scale/arpeggio practice I generally stay away from open notes, because then I am moving in easily transposable patterns and can read/hear intervals as opposed to thinking of absolute notes. Playing a figure in the key of A is exactly the same as playing it in Bb or C with a position shift. Of course there can be efficiency gained using open notes; when I'm learning/practicing parts I use them frequently.
have you ever heard one that didn't absolutely HONK at you?!