I have a Lumia 620, my mom has an iPhone 5 and my brother has an entry level Android phone. Let's see...
My number one gripe about Android isn't its glaring similarity to desktop Windows (Fragmentation, Lag, slowing down over time, widgets, security...), it's not even Google, it's the default font. I know that it's supposed to be robotic, and it's supposed to look cool, and I know I can replace it anyway, but the best you could come up with is Roboto? Really? I say you replace it with Comic Sans and call it a day.
Then again, that's one of the few problems I have with Android. If I did go Android, I'd wait for HTC to bring Sense 5 to their Desire line.
My number one gripe about Windows Phone is how half-baked it looks, and how half-baked Windows 8 is compared to it.
And, I have a ton of gripes about iOS.
I'm fine with any of these three as a daily driver, though. Heck, let's toss in a Q5 for good measure!