I think it depends on the person and the pin.
Personally I only do speaker upgrades on machines I'm selling. In my gameroom, unfortunately, I can't crank the machines, so not much benefit to me.
DMDs...I'm just dipping my toe in. I have a color DMD in my AFM, and one in a box that's destined for my CFTBL.
But I also have a blue DMD in my Tron and a white DMD in my TZ. I don't personally feel like they add much to the actual gameplay ,but they rank on the "cool" scale pretty high!