Yes if it is AS5 definitely follow the burn-in instructions for optimal efficiency.
I have recently found a grease that I now use exclusively (used AS5 exclusively before.) It has a consistency compared to AS5, has virtually the same performance as AS5, but the biggest plus is that it doesn't require a burn-in period:http://www.newegg.com/Product/Product.aspx...N82E16835233069
Also, it's true that you shouldn't count on the PSU to do a whole lot for the rest of the case (cooling-wise) but it does indeed exhaust heat (mainly heat from the PSU though.) As was previously stated, it depends on the case though, as was said there are two styles of PSU mount. Then there's a third style (which is like my Antec 900) to where the PSU is bottom-mounted but you install the PSU "upside-down" to where the fan that's typically on the bottom of the PSU is now on top. So in essence it acts the same as a top-mounted PSU, but it's on the bottom. That type "can" help case airflow, but as previously noted not really enough to count it compared to a case fan. Unless you have some loud PSU that has the fan ramped up all the time...
EDIT: Here's a review comparing the AS5 to the XIGMATEK I mentioned:http://www.hardwaresecrets.com/article/The...ary-2012/1490/5
According to that site, they performed identically, difference being that the XIGMATEK didn't require curing. I might switch to Tuniq TX-3 as again sometime, but the consistency of it is way different, more putty-like than the former two. This post has been edited by SyphonPayne on Monday, May 28 2012, 07:36