Bad, but could be good
I will say from the off, I think this is a bad move for consumers. Apple will have complete control over which network you can use their device on. You can't just pop in a SIM you picked up from the news agents. You can choose from Apple's list of partner networks, i.e. networks which agree to pay Apple.
On the other hand, I believe soft SIMs could be good, if and only if they are operated in a fair and independent manner. They would reduce wastage and allow quicker switching. To do this, I believe they would need to be administered by either an independent party, or under a regulated world-wide standard.
I doubt it will happen any time soon.