It's amazing, you have it run in your icon tray with the temp of the CPU and you hover over it and it displays the Mobo, Case and CPU temps... also, the RPM of the fans, CPU and RAM usage...!
If you're system is custom built, I'd look for the original software made for it. Typically it's readings are more reliable, and the programs tend to work better. I've had speedfan lockup my system a few times. Plus I don't always know what the temps are if they(IE TEMP1 TEMP2...)