I love Sonar, I've been using it forever, great stuff. But...
I hate Sonar, it's complicated, you have to know all kinds of stuff about your windows box to get it to work reasonably well. Sure, it's a problem with most DAWs but Sonar seems to be a lot more sensitive than the rest. Everyone has a problem using it at some point (just look at all the posts here). Yeah, people **** about their issues on all the forums but this one has a lot more technical issues than the others I've seen. The argument that Sonar uses deep windows mojo that makes it much better doesn't stand because Sonar blows up for so many regularly. Yeah, I've got some bug reports that only I can reproduce (missing patch 54) and maybe it's a problem with my graphics card but no one else is missing patch 54 (Pro Tools, Live, Reason, etc).
With Sonar, I can use the best plugins available, Waves, Omnisphere, Komplete, etc and they integrate seamlessly. Unfortunately the stuff that comes with it hasn't been updated in a long time (None of the signature synths have been updated in years). The only new stuff is from 3rdParty vendors. Even if you're old school, good luck finding a good B3 in the std distro.
Finally at last glance, who are the artists endorsing and using Sonar? With the exception of Craig who I've been following since the 80's, who are these guys? When was the last time they charted?