Google might do well to buy Yahoo Finance, if just that part is available for sale. I was just using the Yahoo Finance app on my Android Nexus 9 tablet, and for a few moments I forgot that I was using an Android app; it was so smooth I thought I was using an iOS app. The more great apps like that on Android, the better.
Conversely, the Yahoo Mail app on Android is just an average Android app, imho. The 2015 release was much better than earlier versions, but it still has a long ways to go to be a great app.