Conky’s a neat tool. It’s not as ornate as Gkrellm was back in the day, but it makes up for that in adaptability and a light resource footprint.
Is it necessary when most desktop environments have similar utilities? Perhaps not for most, but I like having the relevant information close at hand yet unobtrusive.
This configuration is fairly simple, though you might need to tailor it a bit to your machine.
If you have fewer than four cores, you can simply delete the irrelevant lines. The mount points for filesystems will be different, so be sure to specify your mount points and drive names.
The network interface on my machine is wlan0. Change ${addr wlan0} to whatever value your machine uses.
The actual file is here. The easiest way to use it is to save it as .conkyrc in your home directory, then call it with: conky -c ~/.conkyrc .