lawajava
I'm just starting on it, but I like what I'm seeing in it. For a long-time Sonar user like me, it's an adjustment. I think it has some really strong aspects.
Sonar was my first DAW, and has been my goto DAW since forever. A couple years ago I got Cubase 7.5, then 8, then 8.5. I agree that "it is an adjustment". It took me about a month of watching Groove3 tutorials and youtube tutorials to feel confortable with it. I also have Studio One 3 and Mixbus 4, and am now demoing Reaper and Mixcraft. My opinion, and this is very subjective, but my opinion is that of these alternatives to Sonar, Cubase is the one that is actually an upgrade , more complete and a step up. As Larry noted, the midi features are great. Studio One and Mixcraft are much easier for the transition, but Cubase was/is worth the effort.
My biggest complaint about Cubase is the GUI--for such a pro software, it's general appearance is more like a flashback to the early days of DAWS; I wish it had the skins/theme modifications that Sonar and Reaper have.
I have never regretted getting Cubase as my backup to Sonar. I plan to continue using Sonar until it no longer works, but Cubase is my backup, and I will be spending more and more time with it.
If you have access to Groove3, it would be worth taking a quick tour, just so you can see what it has to offer. Just my 2cents.