I added the heat sinks that Vorta linked to earlier - and as Tony the Tiger would say, "They're Great!"
I used Arctic thermal adhesive - not thermal paste:
http://amzn.to/1dYPRywI figured that I would leave them on either way, so might as well stick them on for good... The adhesive is the two part kind, so a bit of a pain but nothing major. I cleaned the surface first with Isopropyl alcohol - I prefer these wipes because the wipe doesn't leave any fibers, it's 99%, and they don't skimp on the alcohol:
http://amzn.to/1Gh8xRHI applied the adhesive to the base of the heat sink, and then just stuck it to the miner - you don't need a thick layer of the stuff, just enough to cover the bottom, so I imagine the thermal paste kit above would be enough to do two miners (or at least that's what I would probably be able to manage). Here's what they look like:
So I have a bit less envy about those lucky enough to get factory ones. I would point out that it took me about 30 minutes to apply them all, so not super long, but not fast either.
As I mentioned above, I'm running these miners in what would best be described as a 'harsh' environment - so it was hot when I test it. This particular miner runs typically about 73/73 - this is with the case mod and the Kaze fan in pull configuration. I got it up and running again and let it roll for about an hour, then checked how the temps were doing, and it was a solid 67/66, so about 6c decrease in temp - of course that's just what the internal sensor says, let's take a look at what Mr Flir has to say:
They're definitely running hot, but if you look at the surrounding areas, they're running much cooler, so they definitely seem to be pulling heat from the board. I would guess that the impact on a case without the airflow being as controlled as mine may not be as dramatic - but with mine I'm forcing air over the sides somewhat evenly, so probably a more pronounced effect.
Either way, if you've wondered if and how much of an effect heat sinks on that side can make, now you know. I would classify the ones I got as somewhere inbetween the nice ones that Bitmain put on some of there, and definitely better than those small silver ones most people put on them.