First - as rigpimp mentioned about discovering the Izotope portal...
If any RX or other Izotope users have not installed the portal - it's a good idea to do so and check every once in awhile. Program updates for the stuff you own will be installed and you'll be notified of other free plugins that may be available.
What's the value proposition for Ozone advanced? How has it been useful?
Larger number of features and many more presets. I like to start with Remove Mud preset for clearing up muddy/boomy rooms and tweak from there. I'm not that hot at starting EQ from scratch and use presets as a bit of a crutch starting point.
I have to add myself to the contingent of non-professional music mastering folks. The pre-sets are a helpful way to start a mastering session.
For users like checht, who are satisfied with RX for separating a vocal stem and reintroducing it to your current music file - the question would be - what do you feel you still need other than what you are getting from within your version of RX. If you're satisfied - you're good.
For me, starting off with the suggestions by using Master Assist, it's kinda like Adobe starting you off with your original file in the Master Rack module. Unlike Adobe Master Rack where you start from scratch with everything, Master Assist gives you a starting point. You can choose to use it or not since you are presented with a preview prior to accepting and using the suggestion as your starting point.
If you do accept the starting point in Ozone, you now are able to stack different modules as with Adobe Mastering Rack which I've not been able to do in RX.
One thing to also keep in mind is that if you're working with 24 bit files and want to use Traders Little Helper to create flac files, you can use RX to export the regions to files in 24 bit. At least the last version of Adobe that I had been using saves as 32 bit float which the version of TLH that I have does not handle.
The other thing I just learned recently in working with 24 bit files for uploads to Lossless Legs is that align on sector boundaries only pertains to files you're converting to 16/44.1 for CD burning. Since you can't burn 24/48 or higher for CD's, sector boundaries no longer come into consideration.