I've been a Cakewalk DAW user for many years, and spent the majority of my time in Sonar 7 and 8 (my current version being 8.5).  I've had much success with it.  Is it worth moving to X3 - will it be a huge learning curve with the Skylight look and feel, and inspector, among all these new terms I'm just getting to understand?  What has been your experience moving from the Sonar 8 versions to X versions?

Don't think twice. Go for it now.

I jumped from 8.5 to X3b and found that it has been well worth it.  Totally enjoy the ProChannel, VST3 support and the stability appears to be comparable to what I found in 8.5.  The bakers have included a couple of 3rd party vendor tools that make the decision an easy one as well.  I think this is a solid release.
 
 -Ken

X3 finally feels like it's better than 8.5, to me, whereas X1 and X2 were just different and sometimes annoyingly so.

Same here....I jumped from Sonar 8.5 to X3....a lot of improvement for me; more stable, easier to use etc. 
 
EDIT: oh...and the ARA Melodyne integration....once you've got it you don't want to be w/o it anymore...

You might find the learning curve steep, but it is probably worth it at this point.

After using X1 for a few weeks I tried to go back to 8.5, and I couldn't believe how awkward 8.5 was. And now with X3 I couldn't dream of going back.
But everybody has their own workflow. 
As long as you are prepared to change some of your workflow and are ready to learn something new, you will do just fine (I think).

I followed the grade patch from 8.5 to X3. X3 is definitely light years more advance than 8.5. Get the Groove3 video or Karl Ross X2 video(9hours) to get you started. Go for it!

Sweet, thanks all for your input.  I'm at a good breaking point with my projects and perhaps the upgrade will get more creative juices flowing again.

It will be a huge learning curve from 8.5 though.