It would also be in Long island City which would provide a huge influx of new workers and move that neighborhood forward in development rapidly. The down side would be that it would push some residents and business owners out but this is simply a fact of life in NYC where on a long enough time line every undesirable neighborhood eventually become desirable simply because of increase in residents and increase in real estate prices. That would also conversely make adjacent neighborhoods more attractive.
As for the tax breaks those would eventually be off set and it would still be cheaper than the amount that was spent on a useless Subway line that took a decade and really added no real capacity where it mattered.