The biggest security feature of BBOS is not being subject to the patriot act.
BB10 is mostly a great system. Annoyingly the niggles are generally things BB6 did or did much better. My concern is they will now never fix them. I was waiting for more to be fixed before I buy a Passport. Now I shall wait for the fire sale.
Text input - auto-correct is inferior to 6 (BB6 'shel' > 'she'l'l BB10 'shell' > 'she'll', and similar, really annoying the number of times 'Oh, hell' has gone out as 'Oh he'll') BB6 the dollar key did the local currency, BB10 it does a dollar. (It was far worse initially, there were no phonetic keyboard layouts for Cyrillic for the first few updates)
Email client - inferior to BB6 (but it used to be unstably so, now it is usable)
WiFi Calling - my old BB had UMA. new one doesn't.
2G override my BB6 device could be switched to 2G only, useful in some areas . The new one is consequently unusable in certain areas.
No timed power on/off (and alarms fail from off) unlike every other phone I have owned. (even a £60 android phablet does it).
These (in increasing order of annoyance) were the show stoppers that prevented me getting a Passport. (The final couple mean I need to carry a second device, if I am staying away from home).
They had been fixing them with updates, my list was several times as long when I first got the thing. My expectation is BB10 going the way of Symbian. (Pulled the plugs before all the niggles were fixed).
I suspect unless either BB fix the worst of the BB10 niggles or the Passport becomes available for £100, I shall stick to the Q5 until it dies.