I was one of the lucky ones to get a 5Gh/s Butterfly Labs Jalapeno unit arrive being able to run at about 7Ghz.
But I found overtime the speed was staring to drop and the temp was going up.
After installing a new fan I am above 7Gh/s and the temperature problem has gone away.
As an added bonus the new fan make a lot less noise too!
It was a lot easier then i thought
When all was said and done I ended up leaving the case off because the new fan didn't fit very well, and the ran a lot cooler.
The new fan I am using it this one: Noctua NF-B9 PWM Cooling Fan
http://www.amazon.ca/gp/product/B006GD3K5C/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1I tested the fan with the air blowing up away from the Jalapeno (this is how the stock fan was installed), and with the fan blowing the air down onto the heat sink. With the air blowing down it kept the device cooler.
If you would like to see some pictures I posed them on Google+
https://plus.google.com/photos/114440247402313521185/albums/5968212940859029105 I have been running at about 7.44 Gh/s for a few days with the new set up. It was only running at 6.76 Gh/s before the new fan.