Yes, the downside is basically offline. When offline the LiveView app doesn't work because it can't update it's DOM. A decent solution I've enjoyed is using Alpine.js. It fits very neatly into the LiveView philosophy and can do nearly all UI updating easily. It still minimizes the amount of JS you have to write but you get good client-side update behavior.

High latency isn't an issue if you do it correctly by using the loading classes and what not so that the user knows they are waiting for some data to load. It's pretty much identical to a typical React SPA that has to show loading indicators while waiting for a JSON call to complete.

You aren't suppossed to use LiveView for every interaction, only the ones that require the server to be involved somehow just like a regular SPA. For pure client-side interactions LiveView has some utilities like LiveView.JS or you can use a lib like AlpineJS.

To me that's a non-issue. How are you going to access a website without internet anyways?

If you're talking about "slow" internet, then use Alpine JS to run truly client-side things in those very rare cases.

Yes and no.

It handles crappy connections ok -- it will auto reconnect as needed.

As far as full offline -- it has interfaces to easily alert the user via UI that they are disconnected, however, just like 99.999% of non liveview apps when you are offline things start breaking (load just about any static page site and submit a form or navigate when offline).