I have tried having the EMP grenade equipped, but in general I don't find enough equipment to make it worthwhile. I was wondering however, does the EMP do any damage to enemies? Also, does it do a short-term localized EMP(as in the kill streak) like effect where red-dots are dead and kill streaks can not be used?
EMP grenades do not do damage to enemies (as in potentially lethal damage which turns their screen red), though it will register as a "hit" on your reticle and cause a very brief stun and weapon jump.
As far as the EMP effect itself, it will affect their HUD as normal EMP killstreaks do (disable radar, red dot sight, and ability to deploy killstreak rewards) for a few seconds.