Pros:
Food - Exploration brought the eastern and western hemispheres together, sharing each others food sources. Nations found the new resources extremely helpful to crop rotation, mass agriculture, and fueling a new economy. Some nations, such as Ireland and the potato, became entirely reliant on these new food sources.
Colonization and Economy - Although this is mainly a pro for Western European countries, it is extremely important. Colonization brought massive development of plantations, boosting European economy.
Cons:
Disease - Nearly 80% of the native populations of the Americas were killed off by disease, especially smallpox.
Enslavement - European exploration brought many racial tensions as Europeans treaty almost any non-white man as subhuman. Natives were often forced into labor under laws, but were short lived due to the effects of disease.