Sonar will work under Bootcamp on a Mac every bit as good as a Windows machine, I've been running it for almost three years without issue.

BUT

To ensure good track count and speedy response I would highly suggest a multiple HDD setup.
In the case of my MacbookPro, I have swapped out the optical drive for a second hard drive which is used solely for reading and writing audio from/to current projects.

I openly admit, I'd much prefer Sonar to be cross platform, but as I've said, under Bootcamp it works very well indeed.