I love the extra large soft cover plain moleskins.  They're the perfect size to really get your thoughts on one page and yet they fold up and fit in my purse so I can take notes on the go.  They open pretty flat, and stay open by themselves, so writing in the center and on the non-dominant page is easy.  The covers also fold back on each other, and provide support when you don't have a surface to write on.  There's a reason writers have been using them for years.  They're a treat to write in.