The sharing options on Instagram are some of the best to because as soon as you have customised your picture, you can post it directly to Tumblr, Fickr, Twitter, Facebook or another social networking site.
They have recently updated the app so you can now rotate your pictures! They have also added a new filter and the interface is slightly different.
Instagram bought by Facebook during September and since then things have went downhill for the company in my opinion. They have fallen out with Twitter since Twitter started its own photo sharing service and I can't imagine the user interface getting much slicker and quicker as it will probably end up like the Facebook app (extremely slow).
Instagram does have some cool stuff about it to through. A company funded by Kickstarter.com made a 3rd party device which connects to your home WiFi and it looks like a digital photo frame. You can set it through a certain hash-tag or through your user profile.
The example the company used was a party where everyone is taking pictures of each other and uploading them to Instagram with the hash-tag of #EllensParty. The Insta-Cube (what the company product is called) then shows those pictures with a hash-tag of #EllensParty on the screen.
Overall, Instagram is probably the most intuitive photo editing and sharing app. And although it is currently only available on the Apple App Store and the Android Google Play store let's hope it will soon be coming to Blackberry 10, Windows Phone 8 and also have a website where you can edit and upload pictures.