I'm using a Leuchtturm 1917 pocket notebook right now, and love it. I have yet to have any bleed-through with either Pelikan or Diamine inks (the only ones I've used in it so far). I do get some ghosting with a few of my pens, but I get that with my Rhodia webnotebook too. The paper is very smooth, and hasn't feathered with the inks I've used.
I plan on ordering some more of their books soon.
Also, I can't completely compare these with Moleskine notebooks, as I've never written in a Moleskine. I have, however, handled them in the store, and the Leuchtturm paper feels smoother, and thicker to me.
I have one of their journals that I've nearly finished, it's about 8.5 x 5.5 the size larger than the pocket. The paper is great and it doesn't bleed through even when I was testing different inks or had a Preppy blurb ink on the page