If you enable DHCP snooping to stop broadcasts between switches when enabling ip helper on those switches, it will allow you to terminate the DHCP broadcasting in the given switch, and send a single unicast onward through the remainder of the network.
This reduces the overhead of re-broadcasting the boot-p broadcasts through the rest of the switches that hold the given network segment, and thus reduces the impact of malicious or misconfigured clients from flooding the entire network segment with boot-p requests.
This will also help you locate the source switch where the device being plugged in is located, as it's local access switch will be the source of the unicast DHCP request received by the server.
If, however, you don't use DHCP, then while not providing these additional benefits, the additional overhead on any given network is negligible.
The Server will reply with only 1 IP address to the several unicast requests as a decently implemented DHCP server must needs track the client requests by their MAC addresses.
ie: If you have 30 switches on the segment, then you will only be adding 30 unicast packets out, 30 replies by the server all with the same IP offer, and 30 responses to the client, which will only reply to one of the offers, finishing the acceptance hand-shake.
Thus, the only real drawback is adding a small number of unicast communications for almost no over-head to the workload of the network, which is a minor matter.
However, as noted, when coupled with limiting the broadcasts per switch using DHCP snooping it moves from merely 'not a big deal if done' to actively providing benefits by reducing unneeded broadcast traffic and limiting DOS via DHCP to individual switches.