I've used the DEV-version as my only browser for the last 20 days, and it works like a charm, most of the times.
The only times I run into problems is on:
a) Youtube, I get these notifications saying that the program has crasched, but it doesn't quit or stop responding - and they do not occur every time either.
b) Pages with forms like this. A few times I get the "The page isn't responding" box.
I really love the Dark Mode and especially that the active tab is the only one in black.
The only thing I miss from the old Edge is:
* Add the ability to preview tabs by hovering over them
* Add the "Set the tabs aside" and "Show all tabs set aside" functions
Also, you really need to make it more square-ish like the old Edge. This looks way to much like Chrome.