I've been an iPhone guy since the 3G, but recently was afforded the luxury of carrying two phones because of my job (sales, company pays for the line).
Given my company requires iOS, I decided instead of carrying two iPhones (or consolidating to a foreign phone number and one phone), I'd try out Android.
Began with the Nexus 4 back in February and quite enjoyed it. Now I'm on the HTC One and think its pretty much the greatest smartphone I've ever used.
Now that I have the two phone lines (plus an iPad mini cellular line I can use for upgrades) I'll be buying and selling to try out new phones as they come out. Generally I'll keep an iPhone, a stock Android and a skinned Android on hand and use two of those on a daily basis.
I have toyed with the idea of grabbing a cheap WP8 to check out that ecosystem - something like the Lumia 521, and also the Q5 to check out BB10.....but I don't really have the disposable income to go 5 phones deep lol....
At this point I really enjoy using both iOS and Android simultaneously and will continue to do so for the forseeable future. My next plan is to sell my N4 (and various accessories) in order to buy a GS4 GE - which I forsee being my stock Android phone (and backup phone/occasional daily driver if I'm digging something different) until it no longer receives updates.
Come iPhone 5S time, I'll likely upgrade my 5 and next year, see what happens with Android. Maybe a new HTC, possibly something else. I just like trying new phones out