The PPSh-41 was produced (all sources including postwar China) in about twelve million copies. It is a cheap basic tube gun, like many others originating in the WWII period. Per Wikipedia:
The PPSh-41 fires the standard Soviet pistol and submachine gun cartridge, the 7.62×25mm (Tokarev). Weighing approximately 12 pounds (5.45 kg) with a loaded 71-round drum and 9.5 pounds (4.32 kg) with a loaded 35-round box magazine, the PPSh is capable of a rate of about 1000 rounds per minute, a very high rate of fire in comparison to most other military submachine guns of World War II. It is a durable, low-maintenance weapon made of low-cost, easily obtained components, primarily stamped sheet metal and wood.
Its job is to throw lots of lead downrange, the bullets arriving approximately where directed. The rate of fire is more than twice as fast as the USA's M3 "Grease Gun." I do not think the high rate of fire was particularly advantageous, but it was an understandable design choice in an era when the Germans' fast-firing GPMG's were thought to be superior weapons. It was a conscious design decision to make the Russian buzzgun run so fast, for all you have to do to slow down a blowback gun is add a little more weight to the bolt.
The PPSh-41 deserves better regard than to just tag it as another cheap old fashioned burp gun. It was produced in vaster numbers than the rest. The reason for the big production numbers is that the thing served well and usefully in combat. Its cartridge, though not the best pistol cartridge of the era, may have been the best submachine gun cartridge, driving its small bullet fast and flat, with good penetration at the terminal end of the journey. The gun worked even in appalling conditions afield. It gave Russian units extra firepower when attempts to produce a really good semi-automatic battle rifle were fruitless
It was a peasant's weapon, but so were the longbows of Agincourt. A well-motivated Rooskie armed with this thing could crawl close and then let them have it, a plan that worked all the way to Berlin.