Hub is being used to let servers exchange heartbeat, Windows load balancing, via crossover cable. Bandwidth requirement for this is minimal (it seems 10Mb should do just fine).
That said, is there technical reason I should bother and replace a hub in this situation?
Since the main player here is a Windows Load Balancing, let Microsoft suggest the best solution when to use a switch or a hub. This depends on the configuration and infrastructure http://technet2.microsoft.com/windowsserver/en/library/12fb5106-d068-4a03-9864-cf5da9e31e851033.mspx?mfr=true