tablet pro

I am not exactly sure how your app works. Is it something that runs in the background and just sits on top of everything? Even if the pro has a stylus, I'd still like the software! Being able to set your own toolbar is something everyone can use. All of photoshop's tools have a key equivalent. You could theoretically make your own bar of the tools you use and shut off the regular one! It'd be nice if you could save "sets". A drawing set, a retouch set, a vector set, painting set, etc. all for photoshop. 
The cintiq is wonderful, but a floating palette like you have is more user friendly than the circle one they give you (and more customizable).

Heck with the app you're making, I could see myself working in InDesign or illustrator more easily too! I'd gladly beta a mac version for you. The thing is, a cintiq generally runs on OSX and is just an attachment, so it'd have to be downloaded software or an app that comes from the OSX app store, so I'm afraid it'd be a whole separate programming thing. The IPAD maybe not, but the desktop probably. The draw though is the mac community. I am a freelance graphic artist and I have ONE client on PC, the rest are ALL mac.