"For what it's worth, my rackets are old-school 100% graphite, with no "technologies" to speak of, and I think they're amazing."
Not to be pedantic, but I don't think there is a 100% graphite racket. If the racket is manufactured using a thermoset process, you have to account for the amount of epoxy which binds the layers of graphite sheets. Even the graphite (carbon) sheets are not 100% graphite. Overall, you may have less than 50% graphite in a racket. This is a conservative guess. I wouldn't be surprised if it's even less than 40%. If the racket used a thermoplastic process, you are looking at less than 35% graphite fiber, no matter what it says on the racket. The remainder is nylon.
"Out of curiosity, have you used any "technologies" that you felt made a difference?"
I think one has to differentiate between technologies (wood, metal, "graphite", composite, etc) and designs (large ports, box frame, large head, rocker system, rollers, "kinetic", etc).
For my use, the "graphite" technology works well. I prefer thermoplastic frames (dunlop max 200g, prince vortex), but there are a few regular frames I also like.
In therms of industrial design, the large ports seem to do what Prince claims, with the foreseeable drawbacks; some loss of control and accuracy. Replace the ports and you regain some control but lose some comfort and spin. I bought the Prince EXO3 Graphite because of reviews on TW, because it simply looked good, and because it was on liquidation. Didn't live up to my expectation.
The kinetic approach (I own PK redondo and kinetic) also seem to work. I think the rationale behind it is plausible. The kinetic rackets are comfortable. How much is it due to the sand inside the frame and how much to a more flexible material is hard to assess without draining the sand out of a racket. The PK Redondo is a comfortable racket, which makes me think that the kinetic might be comfortable even without the sand inside it. The Redondo is definitely one of my favorites (also says 100% graphite on it, though I know that's not true).
The power pads work for me. They definitely change the feel of the racket. I don't think they affect the power or reduce arm strain. Leather grips work for me. No other innovations I can think of. My daily rackets are Dunlop Max 200g Pro. Once I started playing with them I couldn't really enjoy any other racket. The Redondo is relegated to backup with the Head Liquidmetal Radical (nice, weighted at 12.5 ozs though I don't think there any technology there)