The only full featured Instagram client on Windows Phone is now live in the Windows Phone Store.
Unfortunately the app is still in beta, and does not offer a free trial, but of course has ready been widely tested, so at least we know it works.
The app offers the ability to create an account, upload pictures, comment, like, follow, find your facebook friends, but of course still lacks the ability to add filters.
If you want to get it before Facebook demands its removal, grab it from the Windows Phone Store here.
Via Reddit.com