It comes with the massive income to all resources.
It increases your menpower by 50 while decreasing your fuel by 50%(was around 50% last time I've seen the ability).
This basically means you can just send waves of men to their deaths. No need for retreat. The ability "Hold The Line" also gives all units massive stat upgrades, which potentially means a long line of defense of literally meat shields. They can stave off the opponents simply by lobbing men at them.
You'll outnumber opponent in early game, you'll loose attrition war in mid/late game due to not being able to preserve vetted squads. Limited fuel won't allow you to get enough armor, you'll get crushed.
Edit: PTRS conscripts are heavily favorable to Soviet because Conscripts are cheap and PTRS distribution means you can have several squads with anti-tank capabilities. It's going to act similar to the PPSh-41 that conscripts already have in their arsenal. This could mean skipping tech, which the Soviet already do. The trade-off of starting with M3 and Penal is less AT. Conscripts with AT rifles early can thus negate that weakness and stave off 222 and other light armor. This is only one of the many abilities, so keep that in mind.
You'll loose AI on a squad that already have bad AI and doesn't scale to get a light AT weapon that doesn't do anything to StuG and up. You won't have guards that can button and fight infantry. You won't have shocks and possible KV-8/IS-2 call-ins for late game. You won't have anything outside of SU-85 to fight armor and you won't have anything at all to fight infantry.
Such a WIN doctrines.