I happened to be looking at Broadcom's page for how to enable jumbo
frames and I came across a good page:

It covers how to turn on/off the various features on
netware/windows/linux and I also spotted this

Netware: Checksum Offload is configured by adding the "CHECKSUM=ON"
parameter to the driver load command line in the AUTOEXEC.NCF file. To
disable, change the value to OFF or do not include the parameter, since
the default is set to disable.

It's disabled by default. My understanding is that checksum offloading
puts that function on the nic rather than on the cpu. One of the things
I always see is during backups my cpu is pegged at 100%. I'm thinking
ok every little bit helps if I can get it off the cpu.

So the question is, any reason why you would not want to enable this?
It's enabled by default on windows servers.