Were war crimes common on non-german, non-russian civilians?
Given that half of Poland was taken over by the Soviets in 1939, and before that Poland and the Soviet Union fought a bitter war in 1920, I'd say you wouldnt have been thrilled. Having said that, there were enough Poles willing to fight for the Soviets to create several armies in the 1944-45 timeframe.
You would probably greet them with open arms.