Apart from the odd glitch with installing (which was most likely down to the Cakewalk server being overstressed with everyone downloading), CbB installed without issue for me [edit - once it had downloaded].
As scook says, the "smoothness" is more to do with issues people have had with CbB reverting to demo mode.
Just to be clear, CbB installs alongside your Sonar Platinum install and will inherit your current Sonar settings.
Since installing CbB, Sonar Platinum still works exactly as it did before, and I can swap between the two without issue... although this is not something I've found the need to do, as CbB loads all my previous Sonar Platinum projects perfectly.
I seriously doubt you'll have issues with switching to CbB - and like I said, Sonar Platinum will still be there alongside it if you do have issues.
M.