My use of the conditional move is similar to Ponz111's entry. I will usually see a winning line and will input that line or it is an obvious recapture or something to that regard. i attempt to think things through as much as possible. If a player makes a move differing, then I adjust my plan accordingly.
That is one thing that I attempt to do is create a long range plan and continue on it as long as possible unless my opponent makes a move to threaten in the position, then I will attend to that threat and continue upon my original plan as much as possible. Sometimes it requires shifing priorities as a key piece is gone but then again, so is one of my opponents usually as well.
I think there might be in some minds a thing that plays on them saying, "if he/she is seeing a move that i have played and then another 2 or 3 moves beyond that, I am not gong to get anything past this guy" or something to the effect.
As to real benefit, save a forced continuation of exact play or obvious move, there seems to be little other than a way to speed up the correspondence for one or both players here.
In my game against a team of high rated masters I played a move they were not expecting but after they saw the move they could see a very long and somewhat forced sequence. This was a game many were watching via the internet.,
The team I was playing knew they were lost but if they resigned then the public would be left up in the air as it was a very nice sequence that most the public would not see ahead or understand. So they gave the long forced sequence which I gadly accepted. After thhat the game only lasted a move or two So, in this case, the forced sequence by this group of masters had a purpose of showing the public why my move wins. It was a sac of my knight for a pawn in the endgame and most of the public, at first couldn not understand why I would do such a thing as it looked like a losing move.