How much time would be saved in skipping the request for the IP of a domain name? Would it be noticeable. Before anyone gets to excited i know there could be problems with using an IP as opposed to a URL in web dev like if you have multiple servers, but im just curious.
About the only thing it will do for you is insulate you from DNS failure. When your user experiences DNS problems, your site will be one the few that mysteriously keeps working for them!
You can still run multiple servers and load balance them behind a single IP, so that needn't be a worry. Generally though, there are far less pros than cons to this approach.