I think someone rolling a social skill needs to at least describe what he is trying to do, and what tactic he is using. For a guard at a gate, you need to at least give me something like "I'm trying to get this guy to let me through, and I'm pretending to be a maintenance guy." I wouldn't really reward good roleplay with extra dice, no more than I would give extra dice to someone for describing his martial artist's attack in more detail. But like Top Dog, I wouldn't penalize a player for a bluff that is described awkwardly.
Just like shooting a gun, not every tactic is going to work. Maybe you're trying to pretend you're the boss's nephew and the receptionist knows everyone in his family, or maybe pretending to be a new hire won't cut it because even new hires would be in the database. On the flip side, sometimes unknown factors can make social skills more effective. If you are trying to frame the Sons of Sauron for a botched explosives job your team did, it might be an easier sell if the police chief is racist against orks.
Social skills should be comparatively subtle in their effects, too. The SR5 rules may have potential problems similar to the SR4 rules, but their fluff is an improvement - it implies that social skills are more for PC vs. NPC than PC vs. PC, and their example of intimidation was a lot more realistic than the SR4 one. The intimidated ganger lowers her weapon and is suddenly more amenable to talking first - note that she doesn't piss her pants in fear and then grovel. I think a lot of problems arise because some players and GMs assume someone with high double-digit dice pools auto-succeeds in telling anyone to do anything.
If someone has high social skills/Charisma, though, I would give them more hints and more detailed descriptions - for someone normal, I might just say the Johnson is a bit brusque, but for a face, I might say he seems snappish because something is making him nervous, and that he seems like he is in a hurry for some reason. Also, another intangible is that I would let them breeze through some situations that are a petty annoyance, or take some time and work, for other PCs. Bouncers wave them in, people cross the street to hit on them, etc.