To all app developers out there, check this course out:
I bought it a while back and it's the best UI style course out there, also it's not that long. Three PDFs + three Refactoring UI videos. You will improve the UI of your apps to a professional level just by following some simple steps... Give it a try, it's a bit pricey but I guarantee it's worth it. It is not a referral link and I don't work for them, it's just my honest recommendation to all of you.