U-turn is actually very viable. STAB makes up for its uninvested Attack and U-turn + Volt Switch is a nightmare to handle! Deserves to be the primary 4th option on choice sets imo (over Energy Ball).
It leaves you open to Steel/Rock/Ground Pokemon but you will be U-turning out anyway or blasting them in their weak SpDef with Bug Buzz. It's very easily a 2HKO after a couple of U-turns and rocks. U-turn is a safer choice than Energy Ball anyway if you mis-predict. So yeah, U-turn is a bitch and deserves a place!
It leaves you open to Steel/Rock/Ground Pokemon but you will be U-turning out anyway or blasting them in their weak SpDef with Bug Buzz. It's very easily a 2HKO after a couple of U-turns and rocks. U-turn is a safer choice than Energy Ball anyway if you mis-predict. So yeah, U-turn is a bitch and deserves a place!