I have little brand loyalty with phones. I tend to buy used smartphones off ebay and switch them every few months as the fancy takes me.
I always avoid the newest handsets and wait for them to be discounted.
Over the last year or so I have had 3 HTC and two Sony mid to high end Android phones.
However, when I was planning a trip to America I discovered only the iPhone could pick up full 3G in both the UK and America so bought an IPhone 4.
My next purchase will almost certainly be a Windows 8 phone.
Personally I find each phone and OS has it's own strengths and weaknesses.