In theory it seems interesting ... lets see how in practice it plays out!

good summary!

Is the expectation that only exchanges to run Ark nodes? Hard to imagine it actually scales anything without being extremely centralized due to the requirement to broadcast a large collaborative transaction every couple seconds.

Really well-written article. I like the idea of Ark in the sense that it's a new higher layer with different affordances and tradeoffs. Btc will eventually need a thriving ecosystem of things like this.

Is it still completely vapor at this point, or is there code?

Everyone is so excited for this. Hope it's well-funded and we see some beta code late this year.