Love the first three albums....yeah, some of the "expirements" on the first album drag it down a bit....yeah, some of the "songs" on the first two sides of II sound too much alike....yeah, some of the "heavy lyrics" on III are cringeworthy.....but, man, Kath wailed and their compositions are really progressive, melodic, exciting....and the changes and tricky time signatures are executed so smoothly (a trick they went a little too far with and turned themselves into....well, Chicago).
Anyone into the classic Chicago sound might check out the first side of Chicago VII....twenty minutes of their best fusion and that's where I kind of get off the train. To include Chicago wouldn't be ridiculous, but to include them welcomes some really harsh reviews (remember disco Chicago...remember boring big band Chicago....remember schmatzy Cetera 80s Chicago....these guys made Phil's Genesis sound like Van der Graff Generator).