I just upgraded to Sonar Platinum, and was wondering if there is anything in X3, that is not included in Platinum. If not, I think I'm going to to uninstall X3. I want to clean up my install, and can't see any need for having both installed, if there's nothing in X3 that isn't in Platinum.
 

I'm not aware anything has been dropped this time.  If you want a clean instal, make sure you uninstall X3 BEFORE you instal platinum.
 
Seems obvious, I know, but if it's done the other way around you could cause serious problems.

Depending on whether you need hard drive space or not, I recommend you leave X3 for now. I just discovered and issue Platinum and was able to launch X3 to confirm the problem. It is not causing me to stop using Platinum. I have a DSF Sound Effects package, as sold on the Cakewalk Site. All the presets .sfz's are not loading with Platinum. I then used X3, thinking the project had become corrupted, to see; it works fine in X3 to make me realize this little quirk is with Platinum.
So who knows what else may pop up as Platinum matures. It can be best to have something to fall back on.

I believe Pentagon is no longer bundled with SONAR

Thanks for the replies. I still have X3 installed on my desktop and I should have mentioned that I'm installing on my laptop now. I've already had to reinstall Platinum last night, as the original install through the CCC put my install on my "C" drive, which is not where I wanted it! Got that figured out, though. I always end up with too many folders of the same thing with multiple version installs, such as content, and vsts. Example: I usually create folders before I install for VSTs, Instruments (Amplitube, Dimension, etc), and cakewalk will create it's own folder. (VSTs / vstplugins, etc.)