I've been running this Warlock aggro deck (which is non-murlock by the way) and I've found it fairly common to open w/ Flame Imp vs. Rogue to an empty board (regardless of going first or second).
Assuming the smart Rogue has 2 Backstabs in their deck, they actually have less than a 1 in 3 chance of drawing this card in their opening 4 or 5 cards. Backstab would be the natural reply, especially on turn 2.
My experience is that roughly half the time I get burned opening with this gambit.
What do some of you think about this play?