Here are five compaints that have been reported since the phone's release:
Overheating
Overheating was a problem commonly reported in the Galaxy S3's predecessor, but it seems to be persisting in the Galaxy S3. This is most likely thanks to the phone's thin chassis and plastic back cover, which do not insulate the heat from the battery.
Battery Drain
The battery drain issue has been reported for the international model of the phone. Consumers have complained that the phone uses a lot of battery, even when its not being used in standby mode. Reports suggest that the problem is due to the fact that the phone calculates 50 to 70 percent more power consumption then it actually uses. The problem is being resolved by correcting the value through a software update that will automatically be pushed out onto to the phone.
Some U.S. users have reported battery drainage issues also, when trying to connect to LTE. Here's a report from a samsung Galaxy S3 forum.
"There is definitely some type of bug that is draining Samsung S3 batteries. I can have days where my battery lasts all day with really heavy usage, and there are other days where I start losing about 10 percent of battery life every hour or more. You can tell when your battery is crashing because your phone will stay warm even if you close all open apps in task manager. . I am trying to pinpoint the cause, but it might be when the phone is struggling to connect to the LTE network. "
Microphone Problem
The Samsung Galaxy S3's biggest problem is a microphone malfunction, according to fix ya. Users have complained that the volume levels come out low on the receiving end and the call is not clear. Fix Ya suggests updating the firmware first, and if that doesn't work, restoring the phone's factory settings.
Charging
Samsung Galaxy S3 users have complained that the phone takes a long time to charge and can get stuck on a certain percentage for over an hour at a time.
Wi-Fi Connection
Some users have reported that the Galaxy S3 easily drops signal when connected to Wi-Fi network. The company is working on a fix.