I have interviewed several WWII veterans on this subject and read hundreds of soldier autobiographies and it depends entirely on the situation. The treatment of prisoners varies by country, the circumstances, and of course human emotion.

The countries had different ways of treating prisoners. The Japanese were well known to find those who surrender to be dishonorable. During the Bataan Death March the survivors recalled troops on passing by trucks sticking their bayonets out and decapitating POWs in the night, not to mention the lack of food and water that they gave them. Germany took prisoners took prisoners but also executed many of them too. During Operation Barbarossa, German High Command issued the "Commissar Order" explicitly stating all captured commissars to be shot, for Germany was trying to reduce rival party leaders. The U.S. took prisoners but there were also several cases where POWs were mass executed by U.S. troops.

Soldiers could lose their temper and emotions and execute POW's. In North Africa a officer of the U.S. 9th Infantry Division had an incident when he had a soldier escort a group of 20 POWs back to HQ for interrogation/processing. After a short travel down the road the soldier opened fire and executed them all, for it turned out that the soldier he picked was Jewish. The Officer said he also choose to not report it because they were getting ready for a push in Sicily and he "needed Everyman he could get". Another soldier interview they talked about how his best friend was chosen to be a point man for a short recon with the officer and Sgt. when his friend got "chewed in half" by a German machine Gunner who then promptly raised his hand and surrendered seconds after killing him. He said that the new inexperienced office took the German prisoner which angered him, and their old officer that the new one replaced would have shot him on the spot. He said that he still regrets it to this day that they didn't kill the German. I have also heard several interviewed Normandy vets that they would just kill the S.S. for they were "nasty B*******". In the Biscari Massacre where U.S. soldiers executed 71 Italian POWs in cold blood, General Patton said "I told Bradley that it was probably an exaggeration, but in any case to tell the Officer to certify that the dead men were snipers or had attempted to escape or something, as it would make a stink in the press and also would make the civilians mad. Anyhow, they are dead, so nothing can be done about it." Patton's opinion later changed when he found out the real facts and they decided to try the men culpable. Of the men who were culpable it was argued in their defense that they were operating under fatigue and emotional distress as well as following their generals orders that "prisoners should be take under limiting circumstances". The men were tried and both were eventually sent back into the war. With these first hand accounts it shows how hard it is to say the frequency that these events happen as it can be covered up or chosen to go unreported. However taking prisoners was frequent and most of the time it was done without a hitch, most archival footage I've seen has the POWs and soldiers appear to be pretty relaxed.

The circumstances was also an important deciding factor. The Biscari incident was not the only time prisoners were executed because of orders. During the Battle of Bastogne the Germans infamously killed 84 US POWs in the Malmedy Massacre. The Germans were at the start of a High risk offensive and couldn't risk being slowed down by the massive amount of prisoners they were receiving, so when they questioned the German CO what they should do with them he responded to just get rid of them. The men took it as an execution order, when the officer would later say he ment for the lower officers to figure it out on their own. The massacre turned out to hinder the offensive as the Americans were now afraid to surrender and would rather die fighting. I interviewed a vet that was part of the 176th Regiment that was massacred, however he and the men with him were sent to a concentration camp instead of being executed. When the war got near it's end and the fighting became more desperate, a vet said that German snipers started targeting Medics and it got so bad that they lost 3 in one day. At that point they agreed they wouldn't play fair either.

So the answer to your question is yes taking prisoners was sometimes dramatic and emotional for the soldiers, and POWs were very occasionally executed through vague orders and those emotions. The U.S. soldiers I've interviewed with REALLY didn't like taking SS prisoners for reasons of the deadlier encounters they had with them or because they were antisemetic extremists. While prisoner processing did slow down the advancing army, it follows the golden rule of "treat others how you want to be treated", and good treatment of prisoners might encourage more of the enemy to surrender rather than feeling backed in a corner.

I hope this didn't stray too off topic, but I do find that the stories and events paint a good picture.

Sources: First hand Interviews with countless WWII USGIs And a bunch of books on firsthand accounts of the Italy and Bastogne fighting.