I like pieced backings, mostly because I like to use up the extra blocks and strips and chunks of fabrics which didn't make it to the front of the quilt. And because it's interesting and fun to have a secondary design.
On occasion, I've ended up liking the pieced back better than the front.
I do know that many non-quilters really dislike pieced backs. I just did the quilting on a collaborative project and the woman who we were making it for was very adamant that she didn't like "those weird and cheap" backs that are all pieced together. She was willing to pay $50 just for backing fabric that wouldn't need any piecing at all. Shrug. Her money, her choice.
RST
RST