I messed with the demo some, kinda like 'haha let me see this ridiculousness'.. but I came away really impressed. It sounds a bit different than other limiters I've heard, something very solid and pleasing about it. And loud, of course. The simplified, cheaper version they have has 'that sound' as well though.
My take was that I simply can't justify the expense, but it's probably worth the asking price. I'd take this over Ozone any day and it's not like that is so much cheaper.
If you have the cash you should consider a fully hardware mastering chain.
And then, have fun running EVERYTHING through it. You music, other people's music, the sound from a movie you're watching... everything. If a record you're listening could use more bass or sparklier highs, go correct that for your listening pleasure... If you're listening to a podcast with five different people using different mics and streaming at different levels, go squash and tame that shit and make it listenable... If you're listening to a war movie at 2 am with super quiet bits and super loud bomb sounds, go even that crap out so you don't wake the gf when bombs go off yet you can hear bits of whispered dialog.
My point is: invest in good processors, practice, get good and fast and confident. Become a fucking pro.
"The processor that no serious mastering engineer can do without" <<< FUCKING LOL. Shit like that cracks me up.
If I bought that plugin and had good reasons to buy it, I would probably run it on a second computer at maximum sampling rate, with a midi controller that is exclusively dedicated to it. Get so used to it you don't even have to look at the interface anymore.
One thing about mastering is that you want to get quick at doing it. You want results before ear fatigue kicks in. That is so so fucking absolutely key IMO.