I'd like to just add my two cents. I registered in the forum, just so I could do so.
When I purchased v18, I fully expected that the UI would be made native before a v19 came around. Quite frankly, I haven't even used 18 because the UI is horrendous in the mac environment. There's honestly no way I'll pay a dime for v19. I'm a former windows user and truly love the app on that OS, but v18 is so far from being useful for me, that I'll honestly feel like I've been ripped off if you charge me for the upgrade. Essentially, you'll lose a mac user. I doubt I'm the only one who feels this way.
I hope you folks do the right thing by us mac users.