Personally, I have an iPhone 5 and as it is now starting to suffer hardware problems (my model has both the "lock" button failure and the premature battery death problems) I had considered using the BB exclusively. On the plus side, the Z10 battery lasts all day -- ALL DAY -- the UI is very modern and usable, and the capability to use up to a 128 GB SD card is nice compared to my iPhone's locked in 16 GB which I constantly have full.
The downside which keeps me from going to BB is still apps. I don't have many iOS apps but what I realized I do have that I cannot replace on BB OS are: native Gmail client, Amtrak (I do a lot of train travel), online banking, Netflix, PBS Kids (for the little ones to use at restaurants and such), and iTunes (seamless sync of music collection). I know some of those apps have substitutes or workarounds, but I will be frank: I don't want to have to f*ck around for it to just work. That is why I left Android after having one from 2010 - 2012 for the iPhone, it was too much crapware and hassle with my music collection.
That's my story, so feel free to "Ask a BlackBerry User Anything" and I will give you my two cents.