Bob
I have not used one myself, but I know people who have. I assume that it is one of the multi pass backs. If so then they are great for some things, not so great for others (kinda like film really....). The people I know are product or catalogue photographers and an architectural photographer. They like them for the immediacy of feedback and the (eventual) decline in cost per image.
The qualms that they have are for anything with movement in them, candle light is one example, leaves moving another. Apparently you don't get a blur but three separate (RGB) images ..... looks kind of weird, part of an image out of registration.
As for copywork, I'm told they great at it.
Like anything there is a learning curve, but something I am sure you can handle.
Can see myself with one one day on my 5x4, when I have a lot of spare cash.....