This application, Chordmaster, is for the Iphone. It is basically a library of how to play guitar chords in different positions, as well as deciding which chords will work together musically. This is an Iphone application, and as such, it'd be surprising to find any compatibility issues. The instructions on the website make using this software very clear. The setup is as easy as downloading the application and running it. There aren't exactly a ton of functions on this application, so using it is pretty difficult.
I have never had a problem with this software, it's not exactly the most complex piece of machinery in the world, so I can't see how anybody would have a problem with it really. The configuration on my machine is always stable, it's not too hard for the Iphone to use any app. The performance I get is fast and reliable. I've only had this thing for two weeks but I'm already a pretty big fan of it. It really is comprehensive, and when I'm sort of stumped by a lead sheet (an increasingly rare occurrence, but an occurrence nonetheless).
I think that the primary audience for this device would be young players with Iphones. Or even old players who need refreshers on chord shapes and inversions. It's actually cool when sitting on a train or bus, just looking over chord shapes and getting ideas for stuff. I like this app a lot, it's far easier to use than the old-fashioned charts and stuff. Personally, I have enough experience that I only need to bring it out when I'm dealing with complex harmonic content, like an Elton John or Beach Boys song. But even then it really helps me out a lot, and I'm glad to have it. I recommend it highly.