The time-slow has a separate duration to the other effects; time is slowed for 15 seconds, while the other effects last for 25 seconds. This is still less than plain Psycho, which lasts 5 minutes.
Despite being a combination of Psycho and Jet, Psychojet can only cause Psycho addiction.
Psychojet can be extremely potent when used with a high damage weapon, giving a fully modified Gauss Rifle an astonishing amount of up to almost 500 Damage with 5 Points invested into the Rifleman Perk and turning the Big Boy into a weapon capable of killing almost every enemy in the game with one shot on all but survival difficulty. It also applies the damage multiplier to any extra damage the weapon may yield, such as burning or radiation damage.
When used with Buffout and Med-X, it greatly benefits a melee based character and improves a character's stats to a point that almost any class has a fighting chance in a melee engagement, for example when getting overrun by ferals or mongrels.