The challenge for startups here has been in finding:
a) seed funding, and
b) funding for consumer web businesses
Both areas have seen significant improvements since five or even three years ago. Since YCombinator left Boston in 2009, Spark Capital (one of the main consumer web & seed-stage VCs here) has raised two additional funds of over $800 million. NextView Ventures raised its first fund in 2012 to invest in seed stage deals, and both New Atlantic Ventures & .406 Ventures raised new funds in 2008 to do the same.
Boston/Cambridge is certainly still far from the amounts of funding in Silicon Valley, but we're far ahead of anyone else, particularly when you factor in population.