I believe that the Pathfinder rules have taken what was a pretty good system in 3.5 and fixed and streamlined a great deal of the mechanics. The combat maneuver rules that replace the clunky grappling, disarm, sunder and trip rules make for one simple but effective method for handling special actions in combat. They also gave every class a significant power boost with the addition of new class abilities and more feats!
Many of the feats have also had a makeover. Specifically the multishot feat that previously gave a ranger (or character with the feat) the ability to shoot 1 extra arrow per x in base attack bonus up to y. This was a full round action in of itself that was in addition to the normal full round attack granted by the class level. I ran into this last week and my immediate reaction when I was asked if a player could use it with rapid shot was no. The reason for this is that the original version of rapid shot was a standard action while multishot required a full round action. There was an excellent sage advice article that went out several years back addressing this exact point. There was just one problem with my call though. After some research online on Piazo forums after reading how they changed the multishot feat I started to rethink my original call.
Although not specifically addressed by Piazo staff there has been enough people to get into this discussion that I believe that the answer is actually a very simple one. The new rapid shot feat says to take a -2 to all attacks as part of a full round action to get an additional attack at your highest attack. The new multishot says that you can use it as part of a full round action and if your first attack hits you roll the arrow damage for the arrow type (only the arrow not strength or magical bonuses such as flaming) twice. Did you catch that? Both say they can be used ‘as part of’ a full round action. This means that not only can they be used together, they can be used together whenever making a full round attack action.
Similar changes to the rules such as how a character (npc or monster) can use the combat maneuvers ‘instead of’ an attack action allow you to make multiple combat maneuvers per each attack action you have when making a full round attack. Thus a character with three attacks as part of their full attack action could make a sundering attempt on an enemy, trip another and use the final to make an attack (or any other combat maneuver including grapple). I think this is pretty darned cool because it allows for cinematic combat and gives players with multiple attacks more choices than just ‘attack attack attack.