In Saint's Row 2, I made extensive use of the cruise control for those drive-and-shoot missions. I seem to remember being told I could use cruise control in Saint's Row 3, but I can't seem to figure out how. How do you work it?
On the Xbox and PS3, it's "Down" on the D-Pad. On the PC, by default, it's CTRL. On consoles, this button is also used to start the streaking diversion and to take screenshots. On the PC, by default it's the "Crouch" key.
To further describe the functions of this button on consoles:
These functions are mapped differently on PC.
The feature's not well publicized, I first learned about it from a random tooltip about 10 hours into the game. The paper manual that came with the game has the buttons listed, which is about all the info that's in the manual, period.