I think many of my problems stem from the fact that I do a lot of real-time PRV editing, so anything that requires extra keypresses or workarounds is super-annoying.
Usually I record a jam or loop, and then listen back to it, fixing note timings, velocities, and pitches during playback. I like to work quickly (since I limited time to devote to music), so keeping playback going is part of that. Any time I have to stop playback I get frustrated.
I found 8.5.3 really good at letting me edit things without having to rewind or stop playback very often. For whatever reasons, X1/2/3 caused more interruptions, and Platinum is even worse.
Sonar can be used in many different ways. I use it as a soft synth sequencer and spend all of my time with the piano roll view on one monitor and track view in the other. I don't use console view, staff view, step sequencer, preset MIDI loops, mastering plugins, autotune, or the majority of the plugins and features which have been advertised recently. Just the piano roll, track view, and soft synth windows, which are mostly Native Instruments rather than Cakewalk. And the occasion CAL script (e.g., adjust note volumes).
Given that I use a *very* limited feature set, I am perhaps more sensitive than other people when one of those features is "acting up". Other people think of Sonar as a HUGE suite of stuff. I basically think of Sonar as a sequencer. I want that sequencer to work smoothly, consistently, and predictably. 8.5.3 was great. It did everything I needed. X1 broke some things for me. Platinum has broken more.
I miss 8.5.3 but I don't want to go back to it, because that would mean all the money I have spent since 8.5.3 has been a waste. I would prefer if Cakewalk would add back what they took away and fix what they broke. I have already posted (multiple times) what specific features I would like to see fixed, so I won't repeat them here. But they are mostly about the same thing: trying to prevent interruptions when editing in the PRV during playback.