Actually scrolling up and down is way smoother with 2 row of tiles instead of 3. Realized that on my 920 a little while back. I kept switching back and forth to be sure but i thought it was a placebo effect. But it's really butter smooth with 2 row of tiles while you can feel the tiny stutters with 3 rows. It's not laggy per say, but you can feel it.
Thought the old layout was weird at first but the tiles look sharper that way. With 3 rows, the tiles are too small and are a little blurry. The background image looks nicer too with 2 rows. It really feels like a "window". Keeping the old layout as well, until i buy a newer wp.