There are a lot of good phones out there, and the right answer for you depends on your use-case. The N9 is pretty fast, easily rootable, has a great community, and is getting more affordable as time goes by.

Also, Android seems to have a nice community (including XDA Developers site), rootable phones, custom ROMs, and a large software marketplace.

Jolla should be releasing its new phone later this year, too.

There seems to be some mystery about Windows 8 software, so since you have some time left to decide, I'd recommend waiting to see how things turn out. The iPhone release should cause prices to go down, so that's another reason to wait.