My favorite apps are just fast.
I'm currently writing this post on the Draft app. All I did was open it up and start writing. All my words get saved instantly.
Instagram uploads photos while we pick filters and write captions. It's so fast it often uploads images with one connectivity bar from AT&T.
It's also much faster to take pictures with Camera+ versus the native iPhone app.
In contrast, Facebook, Instapaper, and Soundcloud are great apps that are slow to load.
Facebook – I can never tell if I get a new mobile DM on Facebook until I rebuff the messages. Shouldn't opening the app rebuff the messages automatically?
Instapaper – All I want is faster saving and faster viewing for newly saved articles. I always open it up on my iPhone and then close it as a reminder it's best viewed on a PC.
SoundCloud – The recording feature is slow to upload files. Like Instagram, this is easily solved in the background while I name and attach a photo to that sound.
Mobile design and functionally are really about the behind the scenes tweaks. As a user, we don't want to see the word “loading.”
App developers need to accelerate app functionality. The best service is simplicity and speed which if done right, go unnoticed.