Should I enable jumbo frame size of 9000 bytes for my NICs?

The deal is this: If everything on your network supports jumbo frames, than by all means, enable it and test. If your NICs are reasonable, and your cabling is without serious problems, you might see an increase in performance. How much? It depends on a lot of factors: how many computers, how good/fast is your switch, network traffic patters, etc. But generally not more than 10% percent in a typical home network or small office network environment.

Here are some testing results from boche.net:

Warning

If you have at least one device on your network that does not support jumbo frames (network printer, SIP phone, etc.) then you cannot use jumbo frames at all. Otherwise you won't be able to talk to that device.