Whether gigabit will be benificial or not depends on what your network needs are. If you do frequent large network file transfers it would be good. If you mainly just do lan gaming, internet browsing, and other low bandwidth things there really isn't a need. Gigabit will not make any difference in those areas.
If you have a gigabit switch and gigabit network cards you are good to go for transfering at those speeds. If you have a router for your internet right now just plug one of its switch ports into the gigabit switch.