Based on my experience with PhD holders working in aerospace engineering, I would view a PhD as an employment warning flag if I was interviewing. Most of the most insufferably difficult to work with people I have encountered have held PhDs in the field they are employed for (one of the others had a masters from MIT).
Obviously not everyone I have worked with who has a PhD has been like that, but it has been a significant percentage.
Entertaining

as you know Chris, I have a PhD (trying not to take the insufferable comment to heart buddy

) and agree and disagree with equal measure. It's the ego that often gets in the way, not the qualification, unfortunately a PhD often involves a drive that most do not want to try....for good reason, a PhD if taken seriously is all commusuing, and often ends relationships.
@C_Claycomb even in my field the ego in others is a pain...I don't make an issue of having a PhD and smile sweetly when I come across others that try to pull rank or take over... knowing that they will go down a few pegs shortly afterwards
It is the professors that are insufferable!!!
Now not all PhD's are the same, and the usefulness is targeted. The main issue with a PhD is that you specialise, so you effectively close doors on further opportunities...and more often than not are stuck on a single career path.
I listen and let everyone have a voice, and for me qualifications means simply that a person can focus for a period of time within a subject area. Now do I look at subject area, yes, I am in a science based team, but I am interested in how they perform as an important variable.
Would I recommend doing a PhD...if you are interested in your subject area, content with a set career path, and you can over preform to standout....then yes
....if you are unsure of your direction / career, reason to do it, or where you can see yourself in 20 years time...then the answer is no
In summary, Masters open doors and I know a few people that have 5 separate subject area Masters qualifications, over getting a PhD.
Looking forward to the next generation, practical skills are more important, and interest.
Just to answer the PhD duration, mine took 3 years, but I did stupid 32 hour days often (worked through the day, night and into the next day), for the last two years while gaining and analysing water, soil samples and botanical data.
Main question to ask yourself is why do you want a PhD?
For me, I thought it was to prove to others that they were wrong about me...only to realise I was proving to myself my worth...I am grateful for that and have never turned back