Coming across Cedric Beust's comments on IDEA going open-source, I thought I'd chime in. Cedric makes valid points, in particular about the unfulfilled expectations after open sourcing a product. As he points out, Jetbrains is unlikely to be flooded with patches and additions from the community, floating them back to the top.
Cedric also correctly identifies that open-sourcing software is an attempt to regain mind-share. He unfortunately qualifies the effort as "last-ditch" which is where I disagree. Companies have to make strategic decisions all the time. Companies live and die by strategic decisions. Who would have guessed 10 years ago that IBM would have survived its transition to services as decided by Louis V. Gerstner? Instead of "last-ditch", in my humble opinion "just-in-time" would be a better qualification for Jetbrains' recent decision.
According to scientific surveys conducted around a glass of beer, people who use IDEA on a daily basis absolutely love it. I am not one of them. But when a company enjoys such a dedicated following, it seems premature to predict its imminent doom.
As Cedric put it, I wish the best to IDEA. I really do.