One small error by the refurbishers can cause major headaches.  The CPU and my disk drives were idling much warmer than they should be (the CPU was 10C above where it should be at idle), and my disks were running about 5C warmer than expected.  The case fan speed was also loud and erratic (spinning to max frequently, and things getting warmer when it did), which is what led me to look at the case fan.  It was installed backward.  In a system like the Dell that relies on a variety of temperature sensors to set the case fan speed, blowing warm air out the front and across the intake air temperature sensor causes erratic behavior.  Also, being that it was spinning up to full speed, when it would do that, it would interrupt the airflow of the CPU fan, since it isn't supposed to be blowing into the CPU fan, but pulling air away from it.Dell fans always go with the label touching the case.  As soon as I noticed that I could see the label when I opened the door of the PC, it was instantly clear what had happened.  Flipping the case fan to the proper direction immediately solved the cooling issues.  CPU idle dropped by 10C, it stopped thermal throttling when the case fan went to full speed, and my drives went back to normal temps.The average consumer would not likely have known or been able to diagnose any of this, and it made the system mostly unusable due to this one minor error.On the plus side, it had an i5-3570, which is just a slightly higher binned 3470, so not really a huge bonus, but it's the only thing keeping this review at 3 stars instead of 1, because airflow is not something where you can just guess and hope.  The fans must be installed a certain way since the system is expecting this, and all its control methods are based on the sensor data and known fan orientations.Otherwise, the system is great.  I just wish they would have paid more attention when refurbishing, because everything else about the system--the packaging, the included keyboard and mouse, cleanliness, Win 10 activation, etc--was top notch.  Amateur hour mistakes can cause major headaches, even for seasoned professionals.  I just hope that someone that doesn't have experience with computers doesn't end up buying one with such a simple but important error, because it really makes for erratic performance with these Dell Optiplex machines and their advanced temperature monitoring and control systems.