http://www.ipernity.com/about/us
I have never heard about them... They have only 25000 users.
Not sure how accurate that number is, they were doing large cleanups recently (plus it says 25000
active users which isn't quite the same thing as all users). They also went through ownership changes recently with the original company going out of business, now the site is community owned by a small non-profit.
iPernity has been around for 10+ years. I have moved there during the first major Flickr exodus in 2009 or so when Yahoo started to censor the Flickr photo content in fairly hamfisted ways and never looked back. I have hundreds of photos there, no problems at all.
You don't get millions of fancy features there but you don't get any of the profit seeking BS common on the other sites neither - tracking, ads, claiming rights to your pictures, having to pay extra for every little bit of functionality.