I am happily using the iOS devices for the past years. I stepped in when the iPhone 4 came and so far nothing has given me a reason to step out of the iOS ecosystem. I have an android tablet (Asus TF300) and that was quite underwhelming experience.
Back when i bought it the quad-core nVidia Tegra 3 chip looked great on paper and in the benchmarks, but actual performance in day to day usage was just nuisance. It was sluggish, things would take forever to load and simple things like browsing and typing in a web-page would be a chore as the tablet would hack and cough its way through the ordeal. I still have the tablet and use it occasionally, but my expectations of the experience are already quite low. To be fair after 3 years my iPhone 4 was also lagging like crazy, but the android tablet did this out of the box.
I have never owned a modern Windows mobile phone, I owned a HTC s710e back in the day, it had windows mobile 6.0. The experience frustrated me so much, it was bad at everything it was supposed to do. It was a horrible as a phone, seriously you could not pick up calls or call anyone without the OS glitching in some way. It was horrible at being a PDA, you could not get alarms to function correctly without tweaking the registry. It was hugely underpowered in CPU and RAM and would freeze up constantly. The thing is I wanted to love this phone so bad because I liked the form factor and the functionality, when it actually worked. I ended overclocking the phone and bricking it within 9 months of purchase. Thoroughly cured of my desire for smartphones I got a samsung G600 and what a relief. It just worked ;)
A few of my colleagues have Windows phone devices and to my surprise I find it quite appealing. All transitions are smooth and slick. The always on screen with time display is a nice touch. The tiles look orderly. So I wonder will it ever entice me to go back?