Remember when you are doing this to either schedule a time for your systems to reboot to complete the update because it is very easy to just click through the prompts and your switches will reboot as soon as the new firmware is uploaded.
When we schedule a large window to do this sort of thing we make sure we manually set a reboot time for all the switches and pre-load the new image hours in advance.
Using the scheduling option is also a way you can manually install the new image you want to use to many switches one at a time but still have them all reboot during a predetermined window. You can this without having Netsight it just takes longer.
We also try to keep our secondary imaged loaded with the latest and greatest software so in case there is a power hit the switch will come back up with the new image and we dont end up having to schedule down time to upgrade it then...