I remember how thrilled I was when I got my first digital SLR camera (because I'd waited so long till the quality matched my affordability) and could manipulate the settings and "Profiles" in camera. WOW! Sharpness! Saturation! ISO! WB! Etc.
Then I learned that pros set everything to ZERO (as a rule, unless deliberately going for a special effect in a shot), and did everything in post. And I learned WHY. (Some sharpening in digital is virtually ALWAYS necessary, for instance. And from there, SELECTIVE sharpening. And so on.)
Then I learned to use the "Creative Zones" -- AV and TV and so on -- but to go to Manual for precise control. Back-button focusing. Etc.
I'd gone from Photoshop 5 to Photoshop 7, and hung out there for years. Then to CS5 last year.
I LOVE the "learning curve." I doubt anybody ever learns ALL that Photoshop can do. But the tutorials from experts like Russell Brown, et al., are wonderful and help me produce consistently better work.
Still, everybody's different, with different needs and goals that seem to constantly evolve. For each new technique I learn, I see new things I missed before, that I can learn to improve.
Depending on the shoot, JPEG is fine, I guess. I just don't personally need to use it anymore. Even for big shoots like parties, I prefer RAW and manual (after consulting test shots in AV, for example, to get certain "default" readings and make adjustments).
Since post-processing is such an important part of my workflow -- even if it's just subtle and minor and quick -- I want ALL the image information my camera can deliver.
That's RAW.