I agree that the wind vector side of the wheel is fine and intuitive. It's the circular slide-rule (reverse side) of the wheel that I find obtuse and unmemorable.
I'm not "in the market" against other apps in the sense that l'm not engaged in any commercial venture. I built my email-based app ostensibly for my own use, a couple of years ago, and keep tweaking it here and there. You mentioned SkyDemon -- it wasn't available on generic mobile devices until the recent iPad release, which I have. I also have a few other apps (AirNavPro on iPad and MemoryMap on both the iPad and Android). They all have pros and cons in my view. Horses for courses. I wouldn't choose one over the other since no one app does all that I like/need. I personally find my email (and GoogleMap) app very useful specific tasks, and I use it alongside the other tools. Just thought l'd share it in case others find it useful alongside whatever other kit they have. That's all !