I bought two of these fans to fit into my Antec 300 case to help keep my ATI HD5850 cool.
I figured if they were the same make as the case I could not go wrong. They were easy to fit myself with a screwdriver, it is recommend that you have intake fans at the front and sides and the outake fans at the back and top. Also remember to ground yourself by touching the interior case first!
There are two sides to these fans. On one side the logo spins WITH the fan and the other side remains static as the fans spins. If you wish the fan to be an outtake fan place the static logo facing the outside of the fan. For intake, face the spinning side facing the outside.
I can not comment on the thermal sensor. It is situated on one side of the fan so I have made both of these fans intakes so the sensor is on the inside of the case. I have not heard them speed up as yet. Though this might be because they are doing a good job keeping everything cool to start with.
The only niggle I have is that the front fan makes a low drone noise, but I beleive this is due to the case interrupting the air flow rather then the fan itself.