My BA have a double-plasma Sarge who leads a two-plasma gun, unpacked ASM squad. It was an excellent Pod unit back when ASM were troops for us. The lack of a power weapon was no problem when using rapid-fire guns. I also have a grav/bolt pistoleer.

But my experiences with them were never positive enough to make gunslingers a theme. When you engage that close, no power weapon really is a drawback. Assault isn't dead in 7th Ed, it's just that competitive players min-max and both Eldar & Tau have JSJ shenanigans. The opportunity is still there, especially if your opponent has forgotten about it.

Inferno pistols' range is a bad handicap. Your upgraded Sarge needs to be at the front of the squad to use them, making him a pricy first casualty.

For thirty points, I'd rather Sarge use lightning claws and toss grenades for a weapon. Claw/storm bolter has become a recent favorite for my Tactical Squads.

 

It would be AWESOME if Pistols weren't all costed 10 points more than they should be, Plasma being THE biggest offender.
Special Pistols should be 5 points, as they all fulfill different purposes, which is cool.

 

I'd personally make them between 5 and 10 points depending on what kind of pistol it is, but I'd have to say that if you're going to spend the points, a storm bolter and lightning claw are the best options. Better assault capability, still two shots that have better strength than bolter shots, and you get to use them at a higher range too, which means you will probably get to fire them more than once.

Main drawback to pistols is exactly that: you honestly just get to use them once for most units, and there are plenty of times that it's better not to shoot at all. How many times have you decided not to shoot pistols because you were afraid you'd roll a bad charge distance, or been stuck in combat for three turns so you only get to fire the pistol the one time? And paying 15 points for a single extra shot is really not that great.

Now, if you could take a unit of gunslingers, like you can with Seraphim, that becomes more viable, because you're upping the ability of the entire squad by basically letting them charge after rapid-firing and still getting the same attack bonus from two close combat weapons. But outside of Sergeants on suicide Sternguard, there honestly isn't much going for them.

 

if you're going to spend the points, a storm bolter and lightning claw are the best options

This works great for my Tactical squads.