It seems to be aspiring to be a kind of cross between Tumblr and LJ/DW. On the plus side: you can have multiple usernames, and it claims it will never reveal the connection between different usernames. It has reasonably good fine-grained privacy settings, and it says it will contact users before revealing any personal information to law enforcement. And it has tools for blocking and banning people, though I've not investigated them in detail. These are good ideas in principle but I'm a bit skeptical, I want to wait and see if their actual security is as good as their ideals. Still, the multi identity thing could be a major draw.
It's apparently based around communities, though lots of people are creating single-person communities to act as personal blogs. It seems to have pretty good tools for encouraging conversation; by default you can comment on and / or follow posts. It does seem to manage the bare minimum of providing a chronological feed of everything that you've subscribed to, with the ability to filter, rather than having algorithms try to guess what you might find "important". At the moment it's not possible to post public at all; the lowest privacy level is that posts are visible to logged in users, but I believe making it readable without logging in is going to be an option (but probably not the default) in the future.
The site is being run by people with some experience, mostly it seems from Reddit. And it has a certain amount of investment behind it, so hopefully it's not going to just fall over as soon as it gets popular. But equally it needs to offer investors a return and right now its business plan seems basically non-existent. There is no advertising, which is good, but there's also no premium service; instead, they have a system whereby users can offer eachother "tips" (minimum payment $1), and they suggest that people add 10% "to cover site costs" when topping up their tipping accounts. I am very very suspicious of this, because places that have no sensible income stream end up either dying or getting eaten up by Google and Facebook, or at best becoming total sleaze fests. Also, if people are able to make money from "tips", then rights holders are going to get very interested in anyone reposting anything that might even slightly be copyright. And of course scammers and manipulators are going to be attracted, but that's a problem with basically all sites.
Aesthetically, it's a mess. Very cutting edge with everything grey on white. Infinite scrolling pages only. They're "working on" mobile apps, but it seems to be more or less readable on a smartphone. It's terribly terribly cutesie, which is at least better than the horrible hipster thing that was Ello. (Anyone remember Ello?) Posts are formatted with Markdown rather than HTML, and posting images and links is as easy as on modern sites like Tumblr or FB. The site communication style is very cutesie as well; I remember some people were put off DW because denise tends to write quite personally rather than sounding like a distant, objective professional, but Imzy is a hundred times worse. So either sexism will kill the site, or it'll massively attract the kind of people who are very into childish-sounding, very enthusiastic, marketing copy pretending to be human kind of stuff; that does seem to be a successful branding approach these days.
I personally don't think it's the right place for the future of fandom, because of the copyright issues and because it bans "porn". So it still has many disadvantages compared to DW, but the novelty value might just make it the next big thing.
ETA: I created a community for DW peeps. Which magically increased my number of invitations from five to 200, so if anyone is possibly interested in an invite, you can request at the community link. And if anyone's already there, feel free to join it or not.
I prefer comments at Dreamwidth. There are currently comments there. You can use your LJ address as an OpenID, or just write your name.