
As for performance, I've owned a 2010 Merckx EMX-5 and a Canyon Ultimate Slx and I prefer the Sonic to both- I'd say it's a real 'classics' bike without the soft ride.
BB is darn stiff but not in the way that some of the new superstiff bikes (Canyon) don't carry your momentum when you pedal, the bike moves with you.
The ride is a bit rumbly, but never harsh, the good side of the EMX-5. It carries it's speed well on the flat, maybe a slight end to the EMX-5 here, but it's better than the Canyon.
Climbing, it's weight is more like the EMX-5 than the Canyon, but the rear wheel seems a bit closer under your butt so it moves when asked.
Descending is fantastic, it has high speed stability, stiffness, feedback, planted feel, and nippy when needed (EMX-5 falls down on nippiness I think and the Canyon is too flighty for me).
For what it's worth, I saw a 2012 Boson the other day and I'm pretty sure it's the exact same mold as the old Sonic, not sure about the carbon layup etc tho...
http://www.isaac-cycle.com/en/models/boson-2012