I've never really had issues with Sonar as far as stability goes. My reliability monitor on Windows has been a flat line at the top for a good year now. (IOW not a single application failure).
This is practically a home-built machine too with some over-clocking and not something that has been provided by one of the dedicated DAW builders that many insist you will need, I didn't need a professional consultation to get it working either. That's not to say I wouldn't use any of those services if I felt I needed to. I see the vendors of those mostly recommended dedicated machines around as providing a quality service as well as being bona fide and invaluable contributers to this community.
I use several music making applications though and I can honestly state the amount of bugs, and when I say bugs I mean stuff thats there that doesn't work, doesn't work as described or requires me to accommodate bad quality implementations by using workarounds, and actions happening randomly without user any input is higher and has historically always been higher in Sonar than it is in anything else I use.
That isn't any exagerration or bashing (Sonar still plays a part in my toolbox and I enjoy many aspects of it) for the sake of it, it is simply the truth of my experience.
Added to that the time scale for fixes is slower if it happens at all as some issues consistently crop up from version to version than any other vendor is able to apply.
Like I said I'm still generally a content Sonar user and it still forms part of my workflow but ironically the reason I have a collection of tools today is that I got fed up waiting for the Sonar implementations to work.
Take lanes for example a great idea that's existed in many DAWs for a number of years now with X2 Sonar has them but they are not yet quite fully implemented to put it simply. I read the issues some people have with the Sonar implementation of them so far and I can understand why some people are not seeing them as the improvement they should be and are in other apps.
Like I say that's just one example.
I keep reading that all apps. are about the same in terms of quality, it isn't true, fortunately they are not equal in terms of feature set either and that is one area that Sonar still scores highly on, and that is the major reason that I will keep pushing for the quality issue to be taken on fully until it is on a par with what else is available today.