I just tried it and it works pretty well. Awfully slow on my mid-2014 MacBookPro though, especially the variable-view-panel redrawing takes very long (1..2 seconds). But definitely a promising new start compared to the older source-map debugging solution.

Hopefully this will also lead to a 'seamless debugging experience' inside VSCode. It would be pretty awesome to have (for instance) a HTML panel with a WebGL canvas in one VSCode tab while stepping through the C/C++ code in another tab. With a bit of tinkering this would also make a nice shadertoy-style live-coding environment.