Gaucho seems to divide opinion but I quite like it, partly because as an album it has it's own sound, which a lot of their albums don't. Like those pre-Aja mid-70's ones in particular are almost interchangable!
I've heard Nightfly, which is decent and basically sounds like another early 80's Steely Dan record. Haven't heard his other solo stuff yet, or Becker's.
I think the first time I became aware of the band was when they won a bunch of grammys with their first reunion record, over a bunch of much cooler and more relevant acts.
The album itself is quite pleasant, though their old snideness comes across more as smugness.
Like I said, their final one is still listenable and has some good tracks, but is obviously their weakest and laziest album. They maybe shouldn't have bothered.
The second track is called The Things I Miss The Most, and is kind of gross in how the chorus has Fagen singing "the talk... the sex" with this sleazy lisp. Big divorced dad energy.
Have you heard the legend of The Second Arrangement? Supposedly a highlight of the Gaucho sessions that an engineer accidentally wiped, and they abandoned it because they couldn't recreate the original magic.
The demo is pretty good, though it sounds pretty much like a normal Steely Dan song so I don't know why they couldn't finish it: