You can view the pistol (and other PowRep items like it) if you go into a crafting station of the appropriate types (Arms for the Qulaar pistol I think) and click on Experiment and then mouse over the pistol. It shows the item from the top down (scrolling off the bottom of the screen) instead of the bottom up (scrolling off the top like normal).
In general, it replaces the mechanics of every pistol power (your energy builder, two gun mojo, etc) with slightly altered damage + some special effect. Along with a different graphic for the pistol as you shoot it. According to Dev posts in other threads, they've balanced out the Power Replaces so that they are the equivalent of regular +Stat items of the same level for the same slot (your avg dmg from a + X Dex item will be equivalent to the damage from the Qulaar Pistol (with its much lower +Stats) when looked at over time.
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In general, it replaces the mechanics of every pistol power (your energy builder, two gun mojo, etc) with slightly altered damage + some special effect. Along with a different graphic for the pistol as you shoot it. According to Dev posts in other threads, they've balanced out the Power Replaces so that they are the equivalent of regular +Stat items of the same level for the same slot (your avg dmg from a + X Dex item will be equivalent to the damage from the Qulaar Pistol (with its much lower +Stats) when looked at over time.