I think the recent theories about the capacitors going bad because they are just badly made, rather that from the heat, are probably correct. I've played my US Duo for so many hundreds of hours and never had a problem. I cleared Ys 1&2 at least a dozen times, OCCed GOT more times than I can count, finished Startling Odyssey II, Yuna 1, and 2, Nadia, Aim for the Top!2, Flash Hiders, Bomberman, etc etc etc. It works perfectly to this day except for the door switch thing...
Around here it seems to be that people think OG Duos are junk, and the other machines are more solid, but here are a few observations I've made:
My original Duo still works perfectly. I bought a busted Core GrafxII and fixed it. I bought a busted Duo R, and fixed it.
So for me the OG Duo is the strong one.
Furthermore, take a close look at these things:
The OG Duo weighs more than a Duo R. Inside you will find a big chunk of shelding that is welded to the HuCard slot, controler port, and AV ports. This is why the controler port rarely breaks loose on the OG Duo, but gets all bendy on a Duo R.
The drives are the same in a Duo as they are in a Duo R, but they are grounded in two more places on an OG Duo.
The OG Duo has a fuse in it, and the Duo R does not. What happens when the system overcurrents? Same thing as a PCE GT I'd guess...it craps totally.
These are just theories of course, but they are based on experience.