I want to download Windows 7 Enterprise from my MSDN subscription. I can see Win7 Enterprise listed, but it gives me the option to get a key. This isn't what I want - I need a version of the media which will work with a volume licensing key server.
If I download this media, will it magically detect the VL key server and not ask for a product key?
There's only one version of the Win7 Enterprise media. It's not like XP/2003 where there was a separate version for volume licensing and retail. During installation, you won't be asked for a product key. After installation, you will be asked to activate. At that point, if you have a KMS server setup on your network with the appropriate DNS records published, it should be able to find it automatically. Otherwise, you'll have to use the slmgr.vbs script included to manually set the location of your KMS server. You also have the option of activating against Microsoft with a MAK style key.
More information can be found in the Volume Activation Deployment Guide