The overriding consensus is that there are plenty of better pastes than AS5. Noctua's paste that comes with the NH-D14 is pretty good. MX-4, TX-2m and PK-1 are all other popular choices. If you don't mind lapping your heatsink, the absolute best thermal paste you can use is Coollaboratory's Liquid Ultra but, like I said, you would have to get some wet/dry sandpaper and get the aluminum off the NH-D14 base.