Neutral
As with any system, there are fans of MSSQL - bringing MSSQL to linux might allow companies to move to Linux from Windows that otherwise were tied to Windows servers because of MSSQL. Even though "most" sql servers try to be compliant with sql standards, each one always has it's nuances.
I don't think anyone that's already on MySQL or Oracle or etc... would move to MSSQL for Linux if they already haven't moved to Windows server; but it might interest new projects / migration projects.
'bout time really; but what direction does Windows Server take now that MSSQL isn't tied to it? It'll be interesting to see what else comes out of this new Microsoft.