I have to say this is the nicest sonar yet. I did not do much in audio the last few years. due to switching of living locations, kids and jobs.
 
 Did not use X1 or X2, barely used 8.5, I think my last sessions were actually on 7.  X3's work flows are nice, very easy to get used to. Can't wait to see what Platinum offers. My only hope is Cake has some sympathy for me as I just bought X3 on Jan 2nd.
 
Either way I don't think it will matter much, just hoping Platinum is an extension of what I have seen in X3. X3 seem to provide what I need. Looks like all my plugs work fine. I have spend the last 1month setting up my rig, hooking up mic's compressors, you name it. Finally getting somewhere.
I pulled up a mix, a and b, c'ing on yamaha's to Bose to events and loving every minute of it.

FWIW, Platinum more or less is an "extension" of X3 so I believe you're all set there.   IMO, at least from my limited time with it, Platinum is to X3 as X3 was to X2, and X2 was to X1 - it's all about building on the foundation originally laid with X1.  Sure, there are changes going from X1 to X2 to X3 to Platinum, but nowhere near the same extent as coming from pre-X series versions.   So if you'd made that transition, going from X3 to Platinum should be a very nice experience.