The troops were actually very ticked off that they took the Garrand away from them and gave them the M14. They saw it as inferior to the proven battlefield weapon especially if they had been using it themselves in battle.
The M1 was a huge advantage in fact. It was the factor that really changed the face of war from trench warfare to mobile battles. Even more than the tank IMO it made a battlefield fluid because the tanks weren't always around.
A single machine gun can only shoot one direction at a time. If you have enough soldiers to outflank a fixed position gun and those soldiers have enough firepower to get the job done then that machine gun loses much of it's advantage. That's why you didn't see people hiding in trenches like they did in the first world war. It was a rare exception to see a few soldiers or even one soldier flank machine guns in that war. Think Sgt. York. But in WWII you could have the main portion of your men keep the machine gun occupied while a few men with the M1 or a Thompson flanked the position of the machine gun. And when they got into position they had the firepower to take out a machine gun nest in a hurry.
Going back to the Band Of Brothers remember how Winters got his Silver Star? His men followed the German trenches and easily wiped out all the German troops that manned those trenches because they had far more firepower. They flanked the positions of the main defense force guarding those big guns and they were able to take those big guns in large part because of their Garrands. That's a perfect example of the advantage the M1 gave the US soldier. Yes of course it took exceptional strategy and courage but the fact they could fire much faster than the German troops was a big factor.