Unsung hero? Alex Acuna. I saw him play in a small group with Brian Bromberg at Crowder Hall sometime during the period 1983-1986. He was outstanding. His contribution to Weather Report was vastly underrated.
Best track? How could it not be Birdland? Zawinul is immortal for that track alone (well, that and Mercy, Mercy, Mercy). But wait. My favorite has always been A Remark You Made. It's Wayne Shorter's finest moment on the album, and maybe his best of all with Weather Report.
Was Jaco really that great? Uh, yes. Just listen to this album. He was a kid who had only recently joined a group of very seasoned, very savvy jazz pros, and absolutely took over the joint. Next question?
Has it held up over time? Not all Weather Report albums have, but this one, you bet it has.