I have a BigBoard over my ironing board. I like it because it's a big rectangle. It's so much easier to iron backings. With my regular board they get re-wrinkled a bit, but with the BigBoard, not so much.
The down side is that it's bigger and I don't have a lot of room for my ironing board. Sometimes I take it off, but then I have to lean it against the wall, which isn't really much better.