For semi-crystalline polymers, nucleating agents are known to speed up the rate of crystallization in the mold, thereby shortening the molding cycle time.
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QUESTION: Besides cycle time reduction, is the temperature of the molded article supposed to be lower ? If so, why ?
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Any feedback will be greatly appreciated

In simple terms, during part cool down, the plastic starts to crystalize at a higher temperature, crystal form faster, the point at which the part is stiff enough to be pushed out of the mold occurs sooner. At this point the part will probably be hotter than a normally molded part, but have the same modulus (stifness). Other savings can come from shortening the cycle time, using less overall heat. Also a lot of nucleating agents will also act like a viscosity modifier and may decrease the heat needed to reach an optimum molding temperature. So nucleation chemistries change part crystalization to achieve improved transparency, so are targeted to improve cycle times. Polyolefins seem to have the most varieties of additives available, Other chemistries can be used in many non-olefin thermoplastics.