In a minor blitz tournament this week I (white) played Nb6 checking my opponent's king on d7 with the idea that after ...Bxb6 I would play Rxd6 (pawn) check (I had doubled rooks on the d-file), followed by Rxb6 which was protected by a pawn on a5, the combination winning a pawn.
My opponent played ...Bxb6 but after picking up my rook to play Rxd6 I noticed a serious problem: my king on g1 was in check. Had I noticed it before picking up the rook I could play axb6 with no serious harm done. But having picked up the rook I was obliged to play either Rd4 or Rf2 both of which left me a rook down. As my opponent was short of time and there was no increment I didn't resign, but I eventually lost anyway.
After the game my opponent said that had I simply played Rxd6 immediately he did not think he would have noticed he was in check and I would have got away with it. I said that once I noticed I was in check, I was simply too rule-abiding to deliberately play an illegal move even if it was clearly in my interests to do so. (Quite possibly had I not noticed I was in check, he wouldn't have noticed either and I would have won the game.)
I am interested to see what others think about the issue of deliberately playing an illegal move in blitz. Do people think that it is an unacceptable form of cheating, or does anyone reckon that it is OK to deliberately break the rules in blitz if you are willing to accept the punishment of loss of game if caught?
I've made the poll a private poll in the interests of honest answers. I've also made it the most extreme case possible: any legal move will definitely lose, but an illegal move will only lose if the opponent sees it and claims.