In January 2012 comScore reported the site had 11.7 million unique U.S. visitors, making it the fastest site ever to break through the 10 million unique visitor mark.
It actually a cool website. I opened an account there and kinda enjoyed the user interface and how the website works. Found a lot of cool pictures there as well :P
Given the connection to FB (development team) and the visual nature of the site, I'd say it has a good chance of persisting into the future. Now if they can just handle the legal issues (copyright, etc.).
Pinterest has found a niche and offered something a bit different from other sites. Pinterest is also attracting a larger following of female members from what I've been reading, so their demographic is a bit different as well. I'd like to see them continue to grow.