I've used BBM and don't see the hype. Aside from teenage girls who uses all the emoticons they throw in there? I thought BB was 'the professionals' phone? I've used BBM enough on iOS I got into a couple groups and had a couple people try it out with me. The groups would rarely update, and with just plain messaging people meh. Not worth having another app that basically does the same thing as iMessage or regular texting.
I much prefer iMessage because its very simple, and works great on a Mac as well. Now with iOS 8 Beta 5, and OS X Yosemite Im texting non-iMessage users as well from my Mac. Great addition, and can't imagine using anything else. Not that Apple is alone with messaging both from a phone and computer but I love the way Apple is doing this.