I've owned a DUET and it's fabulous I upgraded to an Ensemble and missed the DUET so I skimped a little and bought a ONE, didn't like it at first now I love it as a sketch pad the built in mic is awesome and the inputs are great for either a mic or guitar/bass (one at a time) sound isn't bad it's not DUET/Ensemble preamps but they still sound really nice.
But I do miss two inputs at once like the DUET has. but not for STEREO recording.... what are you intending to record in stereo ? I can tell you the only thing recorded in stereo in your entire iTunes library was the drums and maybe some accoustic guitar - everything else practically is recorded mono - vocals, guitar, bass the dialogue in the movies you watch infact so are the sound effects it's in the mix that everything becomes stereo.. ust wanted to point that out because it's not AM/FM Mono Stereo in recording it's a different situation.
So if you like recording a channel at a time then the ONE is great and you can record your guitar/voice at the same time using it's MONO built in MIC as a first take then overdub the guitar and vocals with your own mic etc one track at a time.
When a DUET comes out with an inbuilt mic like the ONE has which it will I will buy because for me that will be an ENSEMBLE killer.
Also every single album you have in your collection was recorded 24/48 sure they may push them out at 24/96 for an SACD release etc but NO ONE records 24/96 to begin with.
So is the ONE cool - yeah, will the DUET2 be the best thing since sliced bread HELL YEAH !
If you use macs and Logic then stick with APOGEE.