Only for a career in research is a PhD important.
the ONLY enduring downside (which you mentioned) is the lost income.
No need to argue that point, because I'm not arguing against it. Look at the comment that I was replying to:
> For those interested in a career in research and development, a PhD is almost a must.
A PhD is a must for a career in research. It is not a must for a career in development. We use the term "R&D," but those are quite different things. There's a lot less "R" around, and a lot more "D."
When I say that the PhD is "rarely helpful," I do not mean that it is totally useless. I mean that the person who would otherwise have done the PhD is probably a self-starter who would've done other equally-valuable things in the meantime. Different things, certainly. But unlikely to be worse than what you would've done in the PhD. Thus, it is not helpful compared to what else you could've done in the meantime.
For a career in the "D" side of computer science "R&D," it's about your technical skills and experiences. Doesn't matter if you acquired them while doing a PhD, or in a company, or working on open source. This is very different from a career in research, where it is much more important to have a piece of paper with "PhD" written on it.
(also, my first job out of grad school was in industry and had nothing to do with my Ph.D. work)
I was pointing out that the PhD is useful for "research", but not for research "and development."
Agreed. But less so, the other way around.
Which is why development jobs don't reward the PhD enough to pay for the opportunity cost. It counts as 6 years of industry experience -- which you could've gotten in 6 years of working in industry.