9 kills for it was a bit much (7 kills and it'd be a great nuke combo option), but it covered a huge part of the map. I've gotten some crazy multikills from it. Stealth Bomber was also really scary if you were the enemy as you obviously didn't know where it'd strike.
Unfortunately not many used it cause it was too expensive – 9 kills and you had to choose it or the Pavelow, and that was a no brainer choice. Also super cool and weird looking as well. It was just a satisfying killstreak IMO.
I think i've even done SB – AC – Nuke combo before. Weird combo but I have gotten 9 gun killstreaks occasionally.