I used E-Blow as last evasive maneuver last week diving Akula. While I am used to a
progressive emersion this one was an
explosive 
. Instantly broke TA and reached the surface in a nothing.
This resulted in a succesfull evasion of the torp but ended in severe damage taken from surface ships
Usually I did E-Blow for say 10 seconds (when deep enuff) combined with change of course and then disactivated it to remain submerged. Yes it ain't much realistic maybe. On the other hand when else would one use it in DW except for evading?