I am a pretty experienced shooter (I collect and shoot WW2 era military rifles mostly) with some (not a lot) experience with SMGs and the recoil of the SMGs in the game feels about right to me. I've only shot full-auto weapons a few times but I can tell you that it takes a lot of work to keep the muzzle rise under control with even a fairly heavy SMG with a moderate rate of fire. My first full auto experience was with a 9mm Uzi, which compares roughly in size, weight and rate of fire with an MP40. Shooting bursts of 6-8 rounds from the shoulder, using the stock and sights, I would aim at the waist of a police training sillhouette at 50 feet. The first round would hit at point of aim, then there would be a couple more in the chest/shoulder area and the rest would impact over the shoulder.
While I'm sure this could be improved upon somewhat with practice, this seems to be about what you get when you fire a burst from the standing position in the game. In real life, you can alter your stance and pull down with your support hand to compensate for recoil. In the game, this is simulated by pulling down with the mouse when you're shooting, Either way, in real life or in game, it requires practice and concentration.
The other SMG I've fired is a suppressed MAC-10 in .45. Much faster rate of fire, faster even than a PPSh, and very hard to control, even with the long, heavy suppressor attached. Worse than the PPSh in the game. The guy who owned this gun shot it a lot, along with various other weapons, and he couldn't do much better with it than I did.
The problem with controlling SMGs in real life isn't the recoil of the individual shots but the cumulative muzzle rise that comes with full-auto firing. Shooting semi-automatically, you can achieve a rhythm (which gets faster with practice) in which you aim the first shot and then press the trigger again, repeatedly, as the gun comes back down from recoil. The less the weapon recoils, the faster and more accurately this can be done, but it's a whole different ballgame when the gun is firing full auto.
I think the infamous video of the woman running a whole magazine through the PPSh without letting go of the trigger is deceptive. For one thing, she's working pretty hard to keep that muzzle down, and as I think someone mentioned here, just a slight change in muzzle angle makes a big difference downrange, increasing with distance. I'd like to see the same video shot from a rear angle so you could see where the bullets actually impacted. I'm betting they were all over the place.