You know, there's definately some merit to the argument that James and D'Arcy had a major impact on the Pumpkins' sound, but, here's my question - when D'Arcy left, and Melissa Auf Der Maur repleaced her, why did the Pumpkins sound 100% exactly the same live as they ever did with D'Arcy... or in some cases, better? Blasphemy? I don't know. To me, D'Arcy was kind of "just there" and played bass because she was available and didn't suck. Live, she just kinda stood there, like the music didn't even phase her. I mean, I know James comes off as something of an introvert, but you could tell James cared about what he was doing. I never got that feeling from D'Arcy, and maybe that's just me.
From the understanding I have, the whole James issue really comes from James' end anyway. D'Arcy had to go because of her issues, and James took her side, and that was one of the major factors that played into the break-up. Okay, I get that. James and D'Arcy have history, so it makes sense. Billy and Jimmy wanted the band to keep going, but James didn't want to keep going without D'Arcy. Two real choices come up, then - break up the band, or dump James and shake up the line-up again. With Machina not doing well, and all the hassles Billy had with the label over Machina II, it probably led Billy to think maybe the band's time had passed and it was time to end it.
What we have now is probably what would have been if Billy had made a different choice. Maybe the fences can be mended, and maybe they can't, who knows?
Zwan was something complately different. Same songwriter going in a different direction with a signature sound. It's like John Fogerty outside of CCW. Sure, there's a similar sound, but it's not the same as the band that was. Some of that does have to do with the other musicians, but a lot of it comes from the intent and the direction Zwan was going in. it wasn't supposed to be the Pumpkins with new members, or else, it would have sounded like them, but they really didn't. In fact, if Zwan was a Pumpkins album, they actually would have taken an entire step backwards from the progression in sound the Pumpkins made on Adore and thru the Machinas, and made what was, in essense, a pure rock album, and not the synth-rock operas the Pumpkins had been creating up to that point.