So I'm at the subway city portion of the game now, I've gotten the upgraded turrets and sentry bots. I'd used them just a couple of times before as there didn't really seem to be a need for them. I have however just completed the first mission from Foreman Jones in Subway city in which the turrets and drones were very handy. There was one point where I dropped two turrets in a point where they had full coverage then fell back to a corner where they just felled wave after wave of mutants, while I laughed, literally. They seemed kind of useless early on but just came into their own with that mission, loving 'em.

The early ones come in handy with Mutant Bash TV rounds.