The GI Bill was one of the most important laws in American history. The bill had short term impacts. Mainly, it made it easier for ex-military men to reenter civilian society. This allowed the US to avoid the sort of post-war slump that happened after WWI.
More importantly, though, the bill had tremendous long term impacts. The bill created a huge new group of college-educated people; many more than ever before. This helped to drive the expansion of the middle class. The bill also helped ex-military men to buy their own homes. This drove the huge wave of suburbanization that started after the war.
In these ways, the GI Bill helped to create the educated, middle-class, suburban society that dominates the US today.