My verdict: a seductive promise that got lost along the way.
Arc was incredible at the beginning: a browser that truly rethought tab management with Spaces, an intelligent sidebar, and impeccable design. I was convinced.
But it's become too cluttered. Too many features, loaded interface... the experience has degraded. It's still a good browser, but the promise of simplicity and focus got a bit lost along the way.
What I like less: resource consumption, growing complexity, and uncertainty about the business model. The team seems scattered (Arc Max, Arc Search on mobile...).
My advice: if you're on Chrome and everything works well, no reason to switch. If you want to test, give yourself a full week to see if the workflow suits you. Many give up before really trying.