I have to say, as a photo sharing platform, instagram is awful. Can't upload photos from desktop, no native iPad app (WTF?), and whatever compression they use to display my photos seems to really mess with the quality (not really noticeable from a phone, but from a desktop, yikes).
It's great to be able to keep up with people in a more meaningful way, and I did attend a pretty cool live IGTV session, but all in all I don't really like it.
And as others have mentioned, I think, you can just middle-click on a post to open it in a new tab and it wont ask for a login.