I really like that combination! I love the neoprene sleeve and have one on order from Incase (my 3G iPad isn't here yet, so there isn't a rush). For around the house, I will likely go without a cover. If I do decide to get something, it will be the Incase Protective Cover, since I really didn't like how the Apple iPad case felt in my hands. When I leave the house, it's going directly in the sleeve.
Since I don't have the sleeve yet, my only area of concern is how tight the fit is going to be. If it's really snug, then you might not be able to get the iPad into the sleeve with the cover on. Based on the MacBook Pro and MacBook Air sleeves, I would guess that the zipper sleeve will be less snug than the slip one. Let me know how you make out!