Unfortunately, while most of the editor works in all browsers, getting full support is really hard. We're doing a lot of things that get pretty deep in the browser, so we wanted to lock things down as much as possible.
We almost were electron-only to ensure consistency, and can still give you the electron app today. We felt it was better to launch with Chrome + Electron than just Electron for an optional installation-free experience, which is why we only support Chrome.
I'm personally really sorry as an engineer that we don't support Firefox, Safari, and other browsers yet. It's on our roadmap :)
As soon as I saw it was Chrome only, I closed out.
For my part, I look forward to trying the product!
By supporting only Chrome, you're showing that you consider Firefox/Safari/Edge as second class citizens, making it harder to trust that you will keep supporting non-Chrome browsers in your generated code.
Rule #1 is do feature detection not user agent detection. What are you doing that is "pretty deep in the browser"? NaCL? Experimental Chrome features?
If I could drop support for it completely I would open up a bottle of champagne. It truly is the new IE of the web.