I use Sensors-Applet to read Temperatures(Gnome panel), fan speed, voltages etc...The only thing missing is the GPU Temperature,no problem I can see it under the nvidia-settings.Here is a SS:http://img479.imageshack.us/img479/9...adatelaqt8.png
(Left to right:CPU Core Temperature; M/B Temperature; HDD Temperature)
@Jaco : You forgot to erase your user in the Terminal :p:

