I've been using Platinum for about... 30 minutes? And found 4 bugs (2 new, 1 old, 1 probably new).
 
1. Can't drag MIDI clips to the desktop any more. Dragging the same clip from the same project works when the project is opened in X3.
2. Piano Roll, despite there being "many other improvements", still can't remember what size I resized the left-hand column to last time whenever I open it, meaning I can never read the drum map names. This is a real work flow killer since 90% of my use for the piano roll is to program drums. Why give us an entire system to map notes to names if you don't want us to read them?
3. Piano Roll, each time it's opened, decides to show me progressively more and more of this pointless "more realistic piano keys" (seriously, who cares?) until they take up the entire screen, crowding out the drum map names above them. So now I need to do 2 extra things each time I edit MIDI: resize the names on the left, and resize the piano keys area to hide it.
4. Double-clicking on a MIDI clip to open the Piano Roll scrolls the timeline window! It moves to wherever the Now time is. I don't think I ever saw this in X3. Hint: if I open a clip to edit it, I am probably interested in that part of the song, not wherever the song happened to stop playing last.
 
This is very disappointing and a step back from X3 when I was hoping to see improvements.

5. Here's another old one (which I reported for X3 here) except amplified - it has the same "nudge destroys all in its wake" behaviour as before, except now it creates a new clip for the stuff you move. In fact it creates one per nudge! Why?
 
Demo (when you see the cursor flash, that's me pressing Keypad 7 to nudge left.)
 

 
Maybe I'm the only person who edits MIDI drums in Sonar these days but Platinum is low on usability for me right now.

Came to think about a topic the other day that was fixed - he was working in a locked screenset and thereby changes he made were not saved.
 
Thinking mostly about your 2) remark - is the column size part of screenset(that is locked)?

I never use screensets, and this has been a bug that existed before screensets did, as far as I know.

 
I believe #1 comes from running Platinum as administrator, which you shouldn't do anymore (apart from while registering certain elements that require that).
 
 

I can confirm 1) at least.
 
Works in X3 but not in SA.
 
None running as administrator, just normal start.

Hi Ben sorry to hear you are experiencing some problems with the latest release of SONAR.
 
Have you checked the Problem Reports forum to see if any of the issues you have identified have been reported there.  If not you could report them there and then others may be able help and see if they can be verified and reported to cake through the problem reporter page.
 
Hopefully we can get you the help you need to resolve these issues.

Problem 2 is there - http://forum.cakewalk.com/CWBRN26976-Drum-Grid-pane-in-PRV-Left-panel-view-keeps-resizing-m3097955.aspx
And Problem 5 - http://forum.cakewalk.com/CWBRN25395-Nudging-note-events-in-take-lanes-doesnt-work-properly-m3023030.aspx
Maybe I'll make new threads for the others.

Thanks for checking them out Ben and please go ahead and report the other problems please keep each problem to one report it makes it easier to help.