I'd have to say 'no'. I did a DPhil by pure research and had to produce a thesis of original work. That means that I did my own learning with some guidance. My thesis is all about provably secure computer systems (using CSP) and I developed an algebra for reasoning about secure systems.

I've never used any of this stuff.

There are plenty of things that I learnt as an undergraduate that I use, however.

That's one way to look at it, the other is to understand the analytic thinking, rigor, patience, new ideas you get out of it -- these are hard to quantify.

But I think I got most of those things from the undergraduate degree.

I think it's a question of sharpening research skills. It's a qualitative deepening of critical thinking, and the step far beyond passable or great to great and original.

I think it's a bit like comparing high school math with university math. Or like saying that you can program after taking a single programing course. :)

Similar skills can be gained elsewhere, are other skill sets are often needed in industry.

I have to agree with the rest - do a PhD if you clearly want to do research/work in academia. If you're just doing it for the credentials - stay far,far away. You might survive, but you will be utterly miserable.

I'm still an undergrad and wondering the same. Is it ever worth it primarily for the credibility? (outside of academia)