West Bengal Chief Minister Mamata Banerjee says the haste over the rollout of Goods and Services Tax or GST is "an epic blunder". But many in Kolkata say the sooner GST is implemented, the better as GST will end a blot on Kolkata - its infamous multi-crore parallel economy of jama kharchi deals, shell companies and cubby-hole entry operators. But insiders are shrugging it off.