Ironic that I wasn't familiar with this company or their products before today, and having read about both Arc and Dia, including reading this blog post you've linked, the product that makes me want to try it is the one they've stopped developing...

It's still worth trying and using. The developers consider it a "finished product" and I don't disagree. It does lots of small things well* that many browsers (even the self-confessed clones like Zen) don't do out of the box, if at all. Maybe in two years the browser will no longer be distributed or receive Chromium updates, but it exists and works fine now.

* For example, I get a lot of value from renaming my tabs and even replacing their favicons with emojis of my choice. Zen appears to have limited support for this.

Thanks, I will do

It was popular but had no real route to profitability. Hence the acquisition.