Having been a former plane captain on the F-14B, I can tell you that the Super Hornet will be a welcome new-comer to the maintenance crews on the ground. The main difference between them being that the Tomcat was controlled largely by hydraulic systems, while the Super Hornet, as well as the Hornet, use fly-by-wire technology. Not only is fly-by-wire technology easier on ground crews (because there is no fluid leaking), but I would imagine that it would be more reliable in combat as there is probably redundancy built in to the system.
The Super Hornet maintains it's little brother's mission of being capable of air-to-air and air-to-ground operations. It will carry significantly more fuel and payload than the Hornet which was an issue at times with the Hornet. It will be somewhat faster than the Hornet but probably not as fast as the Tomcat was able to go.
As jrklr mentioned earlier, the mission for which the Tomcat was originally designed had gone away. The Navy does not have to worry so much about a long-range bomber threat against it's carriers and other ships. The Tomcat was designed to take the fight to the former Soviet Union's bombers and defeat them before they could launch weapons against our carriers. I don't know if this strategy would ever have worked and I'm kinda glad we never had to find out. Since the fall of the Soviet Union and the abscence of a threat against the United States with a credible air force, the Tomcat was transitioned to handle an air-to-ground as well as an air-to-air mission. Sometimes you might hear the Tomcat referred to as the "Bombcat".
Although the F-14 was successful at performing it's air-to-ground role, the maintenance requirements have become the main issue in finding it's replacement. Parts are become harder and harder to come by and advancing technology will make the F-14 more obsolete in years to come.