Primero was severely undervalued when Northgate moved to acquire. Fortunately for Primero shareholders, Northgate was relatively undervalued as well, so the deal (1.5 NGX shares for 1 Primero share) is quite fair for both sides.
Northgate has had some difficulties with their Australian operations, but if they are able to increase margins and efficiencies they will reap huge rewards. Young-Davidson is still a little over a year from starting production, but with its low cash cost it will provide a solid source of operating income even if gold prices were much lower than currently ($1500-$1700).
With the San Dimas mine Northgate takes over Primero's silver hedge, meaning they have to sell most of their silver to Silver Wheaton. But the deal was restructured to provide Primero with the incentive to increase silver production, and so now NGX will have exposure to silver prices, but primarily between June and August 6th (after SLW's quota has been reached), for the next few years. Primero was also working on tax strategies that would allow it to save a considerable amount of money each year (over $10 million), which, if they prove successful, will add another $100m to the market cap.