I've been using SONAR (well, Cakewalk!) since the 90s when it was on floppy disks from Twelve-tone Systems. I am now using SONAR X3 Producer (64bit) and love it. However with an increase in video work I am considering moving to Digital Performer which is now available for PC. If more scoring-to-video features are in the works for SONAR I would love to know about them and I would stay with SONAR. 
 
Some of the things that are missing in Sonar for me are scoring items like a conductor track, streamers and punches, and
"find tempo" which allows you to hit cue points accurately and easily. I've been using Frans Absil's external program "Film Music Tempo Calculation Tool": http://www.fransabsil.nl/htm/eventhit.htm  - why not incorporate something similar into SONAR? The ability to slide the video track left and right freely would be an advantage as well.
 
I never render video from SONAR and really don't need that. 
 
I do like the expanded types of video files that can be used in SONAR now. The addition of .mp4 helps a lot!
 
So I'd rather not have to face the learning curve of DP and would love to have these few features included in SONAR.
 
Cheers!