My take on this.
I have only been playing around with LWC since it was officially announced yesterday. I am not sure if a broader audience would have a detailed hands-on in LWC unless they were part of Pilot. With LWC announced only yesterday, it still has a long way to go before it can be widely adapted. Going through the documentation this morning, Salesforce seems to be working on quite a few things as LWC is not yet available on all Salesforce Experiences, viz., Lightning Out, or Standalone apps (as of today).
In my opinion, you don't need to make an immediate switch necessarily - it's more about choice of the framework you want for your UI customizations: Lightning Components OR Lightning Web Components, they both can/will co-exist. But over the time and with the recommended approach to go the route of Web Standards, it has to be LWC.
From a commonality perspective, even though the bundle structure of Lightning Web Component is different from Lighting Component, you will still find the markups and JS all around. Primarily the HTML Template and ES Modules.
From Learning curve perspective, I would think as long as you have a good hold of markups and JS, the learning curve will not be that significant. Whoever has worked with Lighting Components, will be easily able to co-relate things going around in Lightning Web Components. However, there will be significant learning required if one is not very familiar with ES6+ JS modules.
Based on my "limited experience", below are the key takeaways when going for LWC:
- Get yourself started with Salesforce DX (if you haven’t already done)
- Make VS Code your choice of IDE. With what I could see on the Spring ’19 pre-release Scratch org, you cannot create LWC from Developer Console
I have a quick run down on LWC on my blog post here, if at all that provides any further insight.