I have two very similar 23% crit EW fast shot builds. I invested Spray and Pray in one of them. Spray and Pray being one of my latest builds, I can't say much about because I only used it for a week. I just have not seen the results I wanted vs 100% DR Metal Armor MII using untargeted shots, and most definitely not against the metal wearing Unity NPC's. I seem to be doing roughly the same damage output with the build without the perk. Burst critical rates have increased, however. I can't confirm this, because I don't have laser gats pouring out of my rear, but I have noticed doing slightly more criticals.
I do want to mention Better Criticals perk is working as advertised. There is a dramatic difference when causing a critical. Knockdowns and instant death's from players and NPC's alike, are more prevalent.