It could be argued that Mentats would use it but they use something else (or in addition to) Spice. In a way, prescience would make plain intelligence pale by comparison but maybe the specific type of intelligence that Mentats need (calculating ability) is not enhanced by Spice.
It can if you are willing to pay the price.
In the prequels, the Guild Navigators are described as having genius-level intelligence - at least the story about Navigator D'murr and his brother suggests this:
When they were 17, they entered the Guild Embassy Building with their mother's influence, in order to take the final rigorous test to be accepted to the Guild. They were immediately separated, and placed in two different sealed, testing chambers. Both were separately sprayed with spice, and D'murr opened his mind. D'murr felt melange pressing into his every pore and cell and envisioned himself as a revered Navigator, expanding his mind to the farthest reaches of the Imperium, encompassing everything.
When D'murr passed, he was ushered into the hierarchy of the Guild, and was told that would have no contact, nor see his family again. Immediately D'murr was given complex mathematical quests and problems to solve, and was immersed into an environment which was over-saturated with melange.
The space-folding and travel is not a magical ability - it requires extremely high levels of skills:
Steersman Grodin spoke on a tangent about the technical aspects of what the chosen student had just accomplished on his interstellar journey, how they had employed high-order mathematics and dimensional changes to peer into the future [...]
D'murr is later contacted by his brother but he has a serious problem communicating on such "primitive level"
D’murr paused, taking time to slide back into the limited manner of person-to-person communication. “I have guided a Heighliner through foldspace, brother. I hold the galaxy in my mind, I see mathematics.
Norma Cenva, the genius scientist behind the Holtzman Engine allowing the space-folding travel was using spice gas to increase her mental capabilities, which started causing mutation and turning her into the very first Navigator.
The Dune Encyclopedia lists a variety of physical and mental state changes but increasing the raw intelligence of the user isn't one of them.
The interaction with the CNS is primarily in the Kohliker-Kramptz center, which controls time-space awareness. In most humans this center is rudimentary, consisting of only a small number of cells (K-K cells) in the central cortex of the brain. Ingestion of spice stimulates the growth of K-K cells so that the individual becomes more aware of his/her time-space environment.
These products interact with T-cells of the immune system, rendering the addict immune to most bacterial, fungal, parasitic and viral agents of disease. Moreover, changes which occur in body cells due to aging or malignant transformation are rapidly recognized and the cells are eliminated. Ingestion of spice also imparts an immunity to many common poisons. One of the most striking results of a diet high in melange is the "Eyes of Ibab," the characteristic "blue on blue" eye color.