Like pretty much anything else, it's not a problem when implemented correctly.
Even if you have hundreds or thousands of machines, it's not that difficult to configure your network switches (assuming you don't buy your network gear at Office Depot) to distribute the DHCP and TFTP across multiple servers -- if you even need to, that is; DHCP and TFTP are two of the most lightweight networking protocols in use.
Like pretty much anything else, it's not a problem when implemented correctly.
Even if you have hundreds or thousands of machines, it's not that difficult to configure your network switches (assuming you don't buy your network gear at Office Depot) to distribute the DHCP and TFTP across multiple servers -- if you even need to, that is; DHCP and TFTP are two of the most lightweight networking protocols in use.