What is promised as a "productivity browser for focused work", is really just a Chrome browser with a sidebar containing pinned apps which are essentially just a way to access those apps in split-view. Is that what productivity means to you?
What Sidekick requires a completely new browser for, can be solved by simply using Chrome or Firefox alongside an extension like Workona.
(Yes, I'm saying that Sidekick Browser is more of a feature than it is a standalone product).
The most promising feature with Sidekick is being able to easily jump between different work and personal accounts from the sidebar, in apps like Gmail, Notion, and Google Drive. For those who are using different Chrome profiles to achieve this currently may appreciate this.
With that, only 2 sessions (accounts) are supported for free, to add more than that, you'll be jumping into a pro tier, and the question is, are you open to paying for these "productivity features"? It's a tough call as to if there's enough value here to justify paying, when browsers like Arc Browser offer unlimited sessions/spaces, and effectively sidebar apps for free.
You'll also never get a mobile app with Sidekick, so if you invest much of your time into building out your spaces, it'll be restricted just to desktop. Now that doesn't sound very productive to me, you? 😅
On this note, if you're considering Sidekick Browser instead, well, good luck noticing a difference between these two, they are quite similar and uninspiring.