I made a few very minor alterations after following the recipe exactly the first time. All of this is just FYI.
With the second batch I skipped the milk chocolate chips. They made the first batch very fudgy, and my preference is a cakey brownie. It is also a great lesson learned to ensure that the cream cheese is definitely softened but also, cutting it into cubes before you blend it is also helpful. It makes it much smoother and easier to spread. Finally, I took the reserved cup of batter the second time around and dropped many more much smaller amounts than the tablespoon size the first time. this just made it easier for me to marbelize it. :-)
GREAT recipe - love it, my husband loves it, and it's worth the home-made effort!