Sonar has some pretty serious MIDI problems IMO. I have a lot of MIDI flying around in my projects - both from MIDI clips to synths, from MIDI clips to plugins, and from plugins that have MIDI output. All kinds of weird things start happening if you use this stuff. MIDI ends up in places where it shouldn't. As one example, I've seen situations in which doing something like hitting mute or solo on one track would trigger a note on a synth on a completely unrelated track whose MIDI input was completely unrelated to the track I hit mute on. Imagine a kick drum on a sampler triggering every time you hit mute on a piano track. That sort of thing. 
 
I appreciate that many have had a very stable, bug free experience with Sonar. But it really depends on how you use the program and what your projects look like. Mine are very synth and MIDI heavy, and I regularly had projects become so corrupted and problematic with all kinds of weird issues that I had to abandon them and recreate them from scratch. 
 
The problem is that many people on the forums have been of the attitude "well that doesn't happen to me, so I'm going to reiterate my opinion that Sonar is the best and most stable DAW ever, and call anyone who disagrees with it a whiner." I can sort of appreciate where that's coming from - I feel a little of that on any forum I'm a member on which someone won't stop ranting about a problem which I myself don't experience - but really, they're extremely valid concerns. Sonar should be able to handle all kinds of projects - there is nothing in the product description which says "only suitable for light projects that contain a few audio tracks with a handful of plugins on each." As an example, I've just finished recreating a project in Reaper that become completely unworkable and buggy in Sonar. The project is so large and FX/automation heavy that it took me over a week of working 4-5 hours a day to recreate in Reaper - yesterday I worked almost 12 hours to finish up the automation. So I have these two projects in Reaper and Sonar side by side with the same number of tracks and the same number of plugins, and I have to be brutally honest - the thing runs 20x more smoothly in Reaper with not one single problem or hiccup. I am absolutely over the moon with the increase in performance and stability, and in the process of recreating this project I didn't encounter one crash or one bug (I'm sure Reaper has bugs, it's just that they are nowhere near as serious as Sonar's). 
 
And in my final year of Sonar use, it developed that horrible problem of resetting plugins to defaults. I've been tearing my hair out to the point of insanity trying to deal with it, and as a beta tester spent dozens and dozens of hours trying to pinpoint how it was happening (with only limited success). This to me is a showstopper bug, and although it doesn't happen to everyone, it certainly happened to a certain proportion of users. Any new incarnation of Sonar is going to get off to a terrible start if it still has these problems. 
 
I don't know for sure why they were never fixed, but I don't think it was because of a lack of coding ability by Noel and the team. I really think it was because they just didn't have the time or resources to deal with bugs thoroughly. I'm sure a certain lack of priorities was to blame, but I have no doubt the new team can fix these bugs if given the time and resources. I'm hoping that BandLab will provide that for them.