I have spent more time on the app architecture than the UI (as is evidenced by looking at the app).  Here are some highlights and some remaining "to do" items:

Highlights:
- dependency injection for the service call (easy versioning)
- Restlet library for JSON services
- GSON deserialization of the JSON service response

To do items:
- Download user profile image thumbnails using AsyncTask
- Option to clear search results
- UI cleanup (styles, reformatting the timestamp, search and refresh icons instead of text)
- Dismiss the soft keyboard when tapping outside the search text box
- Utilize a common logging singleton to standardize logging