There are only two scenarios in which people notice the long snapper. The first is when he makes a mistake. The second is when he plays a team-record 16 seasons and a team-record 245 games and is voted captain seven times.
Patrick Mannelly is the second kind of long snapper.
Now, Pat will tell you that he did actually make one mistake: he botched a snap on a field goal during the oppressively windy game against the 49ers in 2005. That was the game that made Robbie Gould miss a 39-yard field goal wide right by perhaps the width of a second set of uprights.