Coincidentally, I tinkered with my first Observable notebook last night (https://observablehq.com/@rzg/prosthaphaeresis -- don't judge too harshly).

One of the improvements on the computational notebook concept is that it seems to compute a data flow graph so it knows what cells to update when the data changes, without you needing to re-run cells in a particular sequence. The cells can also be out of order.

The editor interface is pretty slick, and I wish it were open source so I could use it in other projects.

(Mike Bostock, one of the founders, is also the creator of D3.js and the information visualization gallery bl.ocks.org. Here's my favorite: https://bl.ocks.org/mbostock/31bd072e50eaf550d79e)