Another point that I think has been understated thus far:
Android, WP, and iPhone's visual philosophies are closer now than ever before. I can only assume this will lead to fewer "ecosystem-exclusive" apps, which I think is a net positive for everyone.
You give way too much importance to the visual part, the reason for some apps to be ecosystem exclusive are technical or legal limitations. Writing this on a rooted Android phone with third party keyboard, through a vpn...
I keep hearing about these similarities, but most seem superficial/only visual. How menu/table UI systems work aren't necessarily similar. How does that help apps get on every system?
Android, WP, and iPhone's visual philosophies are closer now than ever before. I can only assume this will lead to fewer "ecosystem-exclusive" apps, which I think is a net positive for everyone.