Most of the time I don't use one and I like the freedom that gives me. I can play what i want when I want and slip from one tune to the other when I feel like it and just stop a tune in the middle of it if someone wants to talk to me. Plus it's usually better practice not to use a back-up recording. But for some things it's simply necessary and for others it's just a lot more fun. Sometimes I've made my own piano arrangements using Band In A Box, other times I've just done a simple automatic back-up with the same program.
Now, which sounds more classy to you? The automatic back-up recording, where you just write a chord progression, choose a style and let the program do the rest sounds kinda cheap sometimes. The problem with the piano backing is that sometimes it may be hard for people to hear if I'm playing the notes on my instrument or if the back-up tape is doing all of it.
Any thoughts on this would be appreciated.