to Guitarhacker - yes, I understand the simplicity of MP3/Wav and I have these as my quick go-to "plan-B". I've been using BIAB live for about 10 years now and I find the flexibility (speed/key/feel) very useful and have had very little trouble. It probably helps that, as I've mentioned before, my gigs are restaurant-type gigs which are low stress and not so much on stage type performances. I really like that I can pop out of a song to speak to people then jump right back in as it always shows you where you are harmonically. Also sometimes musician friends sit-in and I can change a song to a key they prefer. I know of no other product that supports these sorts of things.