I haven't used it extensively, but it's one of few ways to make a truly functional app using just JS+HTML5- allowing you to skip past Java, Objective-C, etc.
Of course, there are huge prices to pay for that- particularly on the UI front. But if your mobile app is a very small part of your business (as opposed to the primary offering, which it is for many) then it can make sense.
I've actually ended up making an app that's a hybrid of native (for top bar navigation) and one big webview for the rest:
I think it's come out as very close to a native experience- it's just a case of putting the time in to make it so.