Any of the PADI specialties can be a fun learning experience or it can be a waste of time and money. Once again it becomes a function of the instructor not the training agency. I do think its a very good idea to get some additional training before diving deeper than 60'. One thing that seems to escape people is what is deep. My definition of deep is where: Your gas supply becomes more limited because it is consumed faster, your deco obligation becomes greater and most important swimming to the surface is no longer an option. Overhead environments are most troublesome because we no longer can make a direct ascent, deep diving(deeper diving) creates the same problem just as full deco dives do. Even though we can look up and see the surface we can't just swim up if the s*@t hits the fan.
As Mike F. indicated a typical "Deep" class doesn't get into the material that a person should consider. gas mgmt., problem solving and dealing with NN, along with gear config. lights, planning, etc. etc. etc.
Can you get this in a PADI Deep Specialty-Sure you can-If Mike was still teaching PADI you'd might have gotten it from him and I do teach it-but I go into gas mgmt. etc in my OW course.
Can you teach yourself -maybe-is diving deeper and deeper teaching you anything or are you gaining any skills-I doubt it
One of the dumbest things I continue to hear and read is- "I went to 95' and I didn't have any problem"
What I have yet to hear or read is " I went to 95' and the s*@t hit the fan, but I fell back on my training and because I was properly equipped and prepared we worked through the problem and here I am."
Diving deeper and deeper thinking that you're gaining experience and skill without any actual training is poor thinking on the divers part. Get additional training from someone who truly knows what they are doing. You will beat the learning curve, a curve that sometimes can be harsh-M
