Interesting. On paper, it satisfies many of my requirements, but I just hated the last Blackberry device I had... I think I'm going to wait for Ubuntu, MeeGo, and Firefox OS.
The last blackberry device you had ran an outdated J2ME-based OS. The new one is built atop the POSIX-compliant QNX kernel and in many ways (though not all) is better technology than is offered by the competition. Not specs, but underlying capabilities.
I'd suggest trying it out before discardng it out of hand. Also - no reason not to develop for both. Qt apps will run just fine on BB10 with minor tweaking, and I suspect on Sailfish as well.