Yes AS5 is an old favorite and have used it for many years and have also tried many others along the way to see if there was something better.
There is a new compound that has gotten some good feedback and it's called Timtronics. I've bought a small tube and will be giving it a try to see how it is compared to AS5.
Here is a quote from a poster named BrainEater:
"Thermal Interface Material or T.I.M. /heatsink paste/etc .... is designed to fill the microscopic scratches between mating thermal surfaces.It's not designed to correct mismatched surfaces or non-uniform clamping , etc.
Any properly designed /implemented thermal solution should be within tolerance without thermal compound !!
The mating surfaces need to be flat or 'pair lapped'....The clamping/mounting screws need the correct torque.
Start there!!....If you are getting 2 degree improvement with thick/expensive/highC compounds then there are other far more important issues....
I use Silicone Heat Transfer Compound | MG Chemicals
20$ buys you a lifetime supply !!
Don't buy the expensive stuff.It's a myth.You don't need it unless you have a warped HSF or cpu....
Here's a secret ;
Wakefield-Vette | A Global Leader in Thermal Solutions, End-to-End Services with Engineering, Manufacturing, and Supply Chain
Commercial thermal solutions. They have the engineering documentation of what I just said too.Check em out , lotta cool stuff there."
As with all things there will be those that try to sell a gimmick product and it's not that it's bad it's just that they try to name their product in such a way as to seem like it's a great product. When the real purpose is what stated above , to fill the micro scopic grooves and holes that you basicly can't see but are there none the less. That's why the proper way to apply thermal compound is in a very, very thin layer. Too much and it starts to act like an insulator and gives you the opposite of what it's supposed to do.
Shin-Etsu MicroSI X23-7783D is what I'm using, this is the best thermal compound I have used so far. Arctic Silver 5 is good, but that curing time can be annoying (200 hours of using and shutting down your PC). Shin Etsu has no curing time. It's a bit thick, but when you tighten your cooling solution, it'll spread just fine.
i used to se AS5, until i found noctua nt-h1. It gives better temps and has no cure time and is about the same price, this is from experience using it across multiple OC'd cpu's and gfx cards. AS5 is old there are better products out now.
Arctic Silver 5 is an oldie but goodie. A lot of people are moving on now, though, since most of the newer thermal compounds require no cure time (you don't have to wait 200 hours to reach peak thermal efficiency) and are not electrically capacitive/conductive.
MX-4 is one of those newer compounds, and it works great.