You mean aside from the survival of the Soviet regime?
Let me go back to the start. By any count, War Communism was a pretty grim period. To throw out a jumble of indicators, by 1921:
Industrial output and productivity collapsed. Census industry was producing a mere 21% of its 1913 figures
Mass de-urbanisation persisted in the major cities, Petrograd and Moscow having collectively lost almost two million citizens
The rail network was barely functioning. Both volumes of transported goods and the number of functioning locomotives had fallen by 70% since 1913.
Shortages were rife. A third of the average worker's week was spent foraging for food or engaging in the black market. Famine wasn't far away.
And, oh yes, there were approximately 10 million excess deaths from 1917-1922. These were from famine, disease, war, repression, etc.
The purpose of the above is not to suggest that War Communism was responsible for the above but to put it in the context of extremely tough times. The Bolsheviks arrived in power in the midst of a terminal economic collapse, to say nothing of a civil war, that they continually struggled to overcome.
Whether by accident or design, the Bolshevik response to these multiple crises was to fall back on direct 'administrative' measures: state control of industry, grain seizures, coercive decrees, ban on private trade, etc. These ad hoc policies slowly coalesced into what was later called War Communism.
But the Bolsheviks weren't stupid. There were plenty of internal critics of bluntness (dubinushka, a cudgel, to borrow a phrase from the period) of Soviet rule. The bureaucracy was spinning out of control, the economic indicators were worsening and the political opposition was mounting. With the White armies finally defeated there were no more excuses for draconian economic measures and any thoughts of continuing with these were put to rest by the Petrograd strikes and Kronstadt rising of 1921.
In short: War Communism had become both politically and economically unsustainable. This is not the mark of a successful programme.
But were there any successes? Well, the immediate purpose of this 'programme' was simple: keep the Red Army and Soviet power afloat. In this it was successful. In power, the Bolsheviks displayed an unexpected aptitude for state-building. For all the 'shock' nature of War Communism, it served its purpose in (barely) feeding the cities and armies during the Civil War.
A very different measure of success is the degree to which War Communism almost inadvertently birthed the basis of the planned economy that would later become a Soviet trademark. Stalinist industrialisation would self-consciously hark back to the 'heroic' period of the revolution, as it set about dismantling the NEP market.
So, to recap. By any standard, War Communism was not a sustainable solution to the crises of the Soviet economy. Recovery would not occur until the NEP. But in the context of the Civil War, drastic and draconian administrative campaigns succeeded in mobilising enough resources to bring about a Soviet victory. And that was its primary purpose.
Sources
I've drawn from the below for the hodge-podge of indicators above:
Davies et al, Economic Transformation of the Soviet Union
Koenker et al, Party State & Society in the Russian Civil War
Nove, Economic History of the USSR
Remington, Building Socialism in Bolshevik Russia