So, I am really enjoying this driving/navigation app, called Waze and as I am wont to do with things I like, I'm now thinking about how they could improve the user experience to make it even better.  A couple of things come to mind:

• Quick Reports: Right now, on my iPad, I have to click through several options to report something.  The app should learn my most common reports and offer a "Top 3" menu to give me the ability to very quickly click-to-report those things I most often report.  There are a couple of pros and cons to my suggestion, though.  The primary reason to do this is that it induces me to report more often because it's easier to do so.  But the downside is that while an adaptive menu works great for providing the most sensible default (Sensible defaults are a core requirement of good UX), "adaptive" is another name for "changes without warning".  As any good UX expert will stell you, changes to the UI require the user to think before acting and thinking before acting greatly lessens the likelihood of acting.  An alternative could be setting up a sensible default quick-report menu, but then locking it in as stable and allowing the user to modify after it's created.  Then they are in control.  People crave control until they have it.  Then then just want it to work without input.  For that reason, control is a tricky thing to provide in a good UX.
• Modify the reward Algorithm: The app throws out raid candy periodically to gain points.  Its a good way to induce usage.  You've done a good job with choice architecture there.  We are social animals and making the social aspect salient (do I have more points than others in my region?) means making the app more interesting to use.  Social proof is a powerful tool in the Choice Architect's tool-chest.  That said, I don't know how you determine when road candy shows up, but you should consider tweaking the math so that users get slightly more candy at the beginning and end of a given trip.  We are naturally more inclined to remember beginnings and endings.  Ramping the candy up then (and consequently ramping it down in the middle) means making the reward more memorable and salient to me when I'm not in the app.
• Rankings should show who I'm better than: Right now, you show me my overall rank, which is a number showing me where I sit relative to the top.  As a human being, though, I don't care nearly as much about how many people are over me as how many are under.  I want to know that I've defeated 203,711 poor souls, not that I'm ranked 3078 overall.  So, consider changing the rank from a single number to a fraction (You are ranked 3078 out of 203,711 active users) or maybe as a percentile (You are are ranked higher than 74% of active users).  Something like that is motivating! People want to be motivated.  Competition motivates, but we need to know how we are doing in the competition.

There's more that could be done, but that hits the top 3 that struck me on my holiday vacation drive.  Hope that helps.

More on Burying the Sign Up Button

...when they took away the “sign up” button and instead put a “learn more” button at the bottom of the page they got a 350% increase in sign ups...

Choice architecture is a fascination of mine. I find the user-directive portion of user experience design to be one of the more interesting and underutilized aspects of UX/UI work. Too often the concentration is on what looks good or what color feels right. Not enough time is spent on what you want the user to actually do.

When I was DC recently, I took a picture of trash cans. A few people noticed and asked my about that pic in my vacation gallery. The answer is easy. Choice Architecture. They did a great job of it. Here's the picture I took:

Do you see the choice architecture at work?  The goal of the museum was to get people to recycle intelligently.  They could have just labeled the cans "Food", "Recycle", and "Trash".  They would have gotten a few people doing it right and most people dumping everything into "Trash".  Why? Because in Choice Architecture saliency is a key ingredient. If we know that oil is limited and funds terrorism, why don't we all conserve more? Because the ramifications of these facts are not salient at the gas pump or the car dealership. Likewise, we know landfills are bad for the environent, so why don't we recycle more? That fact isn't salient when we are throwing things away.  This signage makes the ramifiations of your choice salient to you.  That salience drives your choices subtly, but powerfully.

• Nudge by Thaler and Sunstein