If you're going to put the OS on a small partition make sure to give a fair amount of extra space for Windows 7 as the winsxs folder can get quite large after you install a lot of software and apparently there is still no safe way to clean it up. Even 30 GB might be pushing it and it can be a real pain in the A to go back and resize partitions to get a little extra space.
Also, whether or not you have a ton of RAM, you're going to want to keep at least a small swap file on your Windows 7 drive as I've found totally removing it can cause problems in certain high memory application regardless of whether or not you have the RAM to handle it.
