when you play multilayer over the internet you are only playing it at your normal internet speed (eg 2megabits per second) 54mbps is considerably more than this and so if you are playing over the internet it wont make much difference at all as the bottleneck is your internet speed.
If your playing over a lan, you will be playing at 54mbps, which is much higher than your internet speed and should be much better.
Wired: 100mbps
normal wireless g: 54mbps
The only downfall with wireless, is the reliability of the connection. if the computers that are using wireless are far apart then packets can be dropped and the connection qualaty is not so great. If they are close and there is no interference then you will be fine.