I have also done this- I use the recipe from Junior's cheesecake book and I do not make a crust. Just grease and flour the springform pan REALLY WELL, and let it cool once it's out of the oven/waterbath, then freeze. The next day, you'll be able to pry it out pretty easily.
I've made cheesecake cakes with 1 layer cheesecake sandwiched between 2 regular layers of cake (which makes for quite a tall cake, I used 9" rounds) or I've done it with 1 layer cake under 1 layer cheesecake (with a larger cake and cheesecake, I think I made a 12" square).
I often use ganache to put the layers together which makes for a very rich dessert. I really liked the idea once I started using it! It's very versatile and delicious- I've made a tiramisu cheesecake cake with cappuccino cheesecake, espresso-soaked white cake layers and mascarpone cream frosting. Also a chocolate cake with cherry-swirl cheesecake, and a chocolate cake with creme de menthe cheesecake, and vanilla cake with triple berry cheesecake- MMM! Good luck!