So I need a sleeve for my new MBP. I don't care about style, as long as its not pink or purple I'm good. I will be using the sleeve in conjunction with my backpack. I want a sleeve that has a vertical opening and no zipper. I am looking at the waterfield sleeves (sfbags.com). It seems perfect for me, I can leave the sleeve in my pack and just slip out the laptop. I'm not sure whether to get the flap or not... What do yall think about them?