I'll do a full video at some point, but essentially, the salient point is that you can have four good-quality HD feeds, for the same approximate cost of one premium webcam.
You have to decide what you want most, and there are some things this setup can't do. But I have a few specific purposes in mind, and for those purposes, you shouldn't need autofocus, and you shouldn't need high frame rates. I can set up several angles and zooms with this. I'm thinking different (seated) speakers or musicians on a stage. There's also no reason they all have to be facing forwards: wide angle stage, two close-ups, and wide-angle audience, maybe?