I've actually spent the weekend playing around with an iPhone 4S and iOS 7.1. It was intended to be an experiment/learning experience in order to stay on top of the competitive advantages of the each platform.
Functionally, however, I've come to realize there's really not that much different about them anymore (beyond the app gap at least), and I think WP 8.1 closes the OS feature gap significantly... it may even surpass iOS in a lot of critical ways.
That said, there's lots of little things about WP that I work around or overlook, and I'm sure with time I'd feel the same about iOS. For example, I HATE the iOS keyboard, and I mean that with the fire of 1000 suns. On the other hand, I hate the lack of a "control bar" on WP just as much, but that's coming in WP 8.1, so no reason to be jealous.
If there's something to be envious about, it's the app gap, but now that Windows and Windows Phone are going to start sharing apps, I have a feeling Microsoft will finally gaining big traction here.