I don’t know if it was a decade ahead, but it was really nice. Well thought out UI, really nice and fluid even on not the best hardware, the address-book integration with messaging and throughout the OS was really nice for its time, and some of the phones were actually pretty good (my Nokia had a great camera compared to most.)

Most important for me, at the time it had by far the best dual-SIM support - with active/active radios and proper management of things like separate default SIM for messaging/calls/data at a time when most Android phones with dual SIM were pretty awful, and nearly a decade before Apple would offer dual SIM at all.

I was genuinely sorry to let my last Windows Phone go.