There are several types of apps that I miss on N9:
1. Instagram - Instago is a great app but it uses the public Instagram API and it cannot upload images. I miss an official and fully working Instagram app. After all I guess Molome is a good alternative
2.Shazam / SoundHound (Unfortunatelly Eyrie powered by EchoPrint is not as good as the popular sound recognition apps such as Shazam and SoundHound)