As a counterpoint, I recently built something in a framework (Rails) that was relatively new to me because the framework had large amounts of functionality available as open source components (info in profile).
I reviewed other options, including technologies that I was more familiar with, but the risk of slower development while I came up to speed was outweighed by the increase in speed to market.
I reviewed other options, including technologies that I was more familiar with, but the risk of slower development while I came up to speed was outweighed by the increase in speed to market.