I love sketching in the 3.5 x 5.5 Moleskine.  I was so resistant to painting in the Moleskines because I found the paper to be of very poor quality.  It is very lightweight and has very little tooth.  However, they were on sale at Deserres and I bought one just to try it.  I was very surprised just how much I like them.  The paper acts like hot press paper in that you can really manipulate the paint on the surface before it dries.  Now, I am hooked.  I still reserve Arches 140 for planned paintings, but for everyday sketching, I really enjoy the Moleskines.  It took me a month to fill my first 30 page journal...a painting a day~!  I started my new journal today.  I am trying the larger format 8.25 x 5 this time.  As you can see, I am not very good yet at planning the size of my sketch on the page.  Hence, the cut off top of the house.  However, I find pleasure in the fact that I am getting out daily and sketching on site.