I have the small one, a little ovr 12" that I use for small things. I can sit on my bed and watch tv while assembling tiny appliques. I use a tiny Clover iron for that, not sure how it would be with a full sized iron.
I also like it to sqaure up small blocks. I think I got it at a Joanne's 50% off sale, but some of the bigger ones are horribly pricey.