Sometimes it's useful to see what's going on inside your Mac, especially when things are going wrong or performance is unstable.
iStat Nano means that obtaining such details has never been easier. Simply bringing up your dashboard will display the iStat widget with a detailed readout of the major components. It's such an elegant and handy widget that it's hard to believe that it's free. It displays absolutely everything, including CPU speed, internal temperature, remaining memory, connected drives, IP address, network traffic, battery status and more.
The widget is divided into various different categories such as temperatures, fans, processes etc. Clicking on one flips iStat Nano to reveal the full details. Everything is performed in real time and there's no delay in between selecting a category and seeing the results.
In the preferences, you can customize the units in which you want readings to be displayed, whether to enable animations and even change the skin color. Possibly the only drawback I found was that the process list is limited to the top five processes and there's no way to kill them either but this is not really the widget's job anyway.
For diagnosis or just for fun, iStat Nano is an excellent widget for giving you a comprehensive readout of your Mac's vital signs.