It depends on what type of well you have. If you have a dug well, it best adapts to coastal areas, and therefore won't be too impacted by salt water. However, dug wells dry up easily during droughts, and there's a great chance of bacterial contamination because they're shallow. Drill wells are much safer than dug wells as far as the water goes, but the water is only good depending on what is going on in the area. It can easily be impacted by that. Hope that helps.
I had well water for years and the pros are the fact that you can be assured there are no chemical treatments or chlorine in the water, not to mention no water bills. The cons can be not knowing what folks are adding to the ground water down the road, which always worried me. Also, since you need electric to run a well pump, when you lose power, you also lose water.