Already covered elsewhere esp in the two stickies up top.
For me.
1) Stuck notes in Machine (and other daws away from Sonar).
2) Lack of sample mangement meaning hard if not impossible get all samples under one folder. When we open samples hard to know where they live (yes it is hidden in the log file somewhere). Right now my files are all over the place.
3) Hard coded log files.
4) Lack of settings section allowing for sample management, custom file paths for sample locations, log files, sample rates etc (why should I have to look up a shortcut key?)
5) Speed of loading. No splash screen making it hard to tell if it's starting or not.
6) Fear it will end up being handled like z3ta+2 for instance which still has stuck note issues and other bugs not fixed.
7) There are a few more specific bugs with the core functionality others have noted.
8) Promises that patches were coming out quickly to fix some of this, we are still waiting.
9) UI when browsing the sample library is way too small.
In the world of modern software I should not need to hack the registry. I should be able to relocate my samples and prog files easily. The silent samples should never have happened (at least it was more or less fixed but still required user intervention and access to legacy folders rather than import to a new folder).I should be able to access settings in the UI and not just shortcut keys, I should not have to work around hard coding.
Above all I assumed I was paying for major improvements in Rapture and Dim Pro. Rap Pro would at least address all the shortcomings of both. That never happened. What came out may have passed as a rough beta but not a final consumer product in the year 2015.