The people in the Friends icon are too vertically staggered. It looks like one friend is apart from the rest. Maybe show one person front and center (the user) with two people behind and on either side of that person.
It’s unclear where the boundaries of the buttons are. Add borders, or a rectangular gradient behind the button.
The colors don’t match, especially the orange people and the background. I’m not sure how to fix it, but I think you should at least darken the button label text, because black matches better than gray, and it would increase contrast against the similar-brightness background.
It’s confusing how a green check represents an app, but a green plus means add a new friend. I think an app would be better represented by a rounded-corner square, or a square with an upside-down “V” cut into it like the silhouette of an “A”.
It looks like there is too much space at the bottom. Make the buttons taller to fill the screen, or show them as 5 items in a list. Showing them as a list would also solve the problem of the excess whitespace next to Find Friends; alternatively, you could center that button, but that might draw too much attention to it.
I have an Android app that I've been working on. The primary purpose is to let users see the apps their friends have so they can discover new ones.
You can see screen grabs @ http://www.appadvocate.com/screenshots2/
But the one that I really need help on is the home screen: http://bit.ly/ackPgK
The most important things for a user to look at are Friends (shows a list of friends and how many apps they have) and Friend's apps (shows a list of apps the user doesn't have but are being used by friends).
And I'd also like to figure out a way to encourage people to invite new friends to join them.