Mix is alright, but not good enough to keep me from missing Stumbleupon. Correct some of the major issues below and I'll happily bump this to 3-star. Add hotkeys so I don't have to wear out my right hand clicking through your website and your add-on, and I'll give you a 4-star review. Add a button to randomly pick a "For You" page, and I'll bump it to 5 stars. It's not even about the actual content at the moment since it is so difficult to actually view it when compared to SU. I mean the old version, it's not quite as bad as the newer WebExtensions version of the Stumbleupon Toolbar, which is a nearly unusable mess.

_TWO knocks for having no way to adjust what content I want to browse after account creation. So you're saying I have to make a new account if my tastes change? IF there is a way to do this, it's extremely unclear to the average user.
_Knock because even though it said I could completely import my Stumbleupon account, the only thing it seems to do is add all my favorited sites to a private collection.
_Another knock for not being able to get to the Mix website using the addon, which seems to have the lions share of the features at the moment (I can only add stuff to my collections and click links on "For You" using the addon).
_Another knock for having ALL email options on by default.
_Another knock for your main feature being able to choose from a series of "For You" websites, but the interface only showing 6 links on a 1440p monitor. Absolutely massive waste of space! If someone is interested enough in Mix to actually install and use it in their browser, you can bet they are VERY INTERESTED in seeing a ton of juicy websites they can visit. 400+ pixel wide tiles is totally unnecessary unless you're on a 4k monitor, and I can't find any way to increase their size or the number of columns. It feels like a phone app stretched to a full monitor, completely wasteful. Changing the scaling of the page is not a good workaround, and the columns don't dynamically fill the space so you end up with a narrow bar in the middle 1/5th of the screen with 12-15 tiles depending on how good your eyesight is. I can't imagine how comical the website would look when viewed on a 1080p screen. Your clients are incredibly important stakeholders, please be aware of ergonomics when designing the website & addon.

What are we at now? -6 stars? Ok, I'll give you 6 stars for actually functioning unlike many other addons in the new [utterly terrible] Firefox add-on schema, another star for the cool drooling logo, and 1 star for trying really hard to improve on Stumbleupon. I see the potential, I really do, but feature wise we're pretty far off right now, and I can't give you more than 2 stars due to the frustrating nature of browsing. And it reminds me too much of Pinterest which is a form of cancer for Google. Simplistic does not mean simple, and unfortunately Mix is simplistic.

Update: Clearing my browser history signs me out of Mix. Also, when I sign back in and try to start using the addon, it kicks off the whole account creation process all over again. Just nope. -1 star.