I have been following this app for some time now, it looks like a mobile version of band in a box witouth much of the whistles. I am as interested in everyones opinion as you are.
I would say that it is a neat app. I have both IOS and Android versions. I can't really say the sound quality is good enough for gigs, but certainly it will make a good practice tool. Onece you join the iReal Pro forum, tons of songs rather chord sheets can be downloaded. I had to pay for the style packs but now they are all included with the app.