Not really, Zendesk has being there since Aug 2011 and the block between 6th and 5th is way better. I walk this block everyday and it changed, for good.
Twitter is between 9th and 10th street, so comparing the changes between 5th/6th isn't really describing what's happening around Twitter. The whole article talks about some transformation that hasn't happened yet. 5th/6th isn't really that safe anyways. Maybe during the day and when work gets out around 5-6PM, but I wouldn't recommend staying out there after 8PM