Edit : Thanks for your answer. The workflow behind those requirements is :
- I set the status of the review link on "Review needed" then I send the review link to my client.
- my client adds some coments then he changes the status choosing between two options : "Changes required" or "Approved". Once he made his choice for the status, he can't change it anymore and can't add comments anymore until I change the status to "Review needed".
- if the new status is "Approved" (and if I allowed it in settings), the download button is displayed.

And all of this without the need for client to log in. I think that, at least for me, it's the best workflow to avoid useless messages, improve communication with the client and prevent the customer from obtaining the final rendering file without paying the full amount due. So the most important in requirements I've made is the possibility to decide when display the Download button for the client, or to not display it at all.

Review : Ok, since several months ago, I was looking an alternative to frame.io. Few days days ago, I started to seek on Appsumo but I couldn't find one. Today, I found Kreatli and it does the job very well and that's the only reason (for now at least) why I bought a tier. So just for this, I already give 5 tacos even if there are some improvments that I would love to see in the future :

- the ability for the client without an account, to see the status of a review link
- the possibility to decide when the client without an account can change the status of a review link (for example : the client can only change the status when this one is on "Review needed", and he can only change it to "Changes required" or "Approved")
- the possibility to decide when the client without an account can add some comments on the review link (for example : the client can only add some comments when the status is "Review needed")
- the possibility to decide when display the Download button for the client, or to not display it at all (for example : the client can download the file only if the status of the review link is "Approved")

By the way, I love the fact that we can compare two versions side by side. That's a function that I have never thought about, but now I know it's here, I think I'll use it everytime. And I also love the fact that once the client published his comments, he can't edit or delete them. Kreatli is definitely worth it.