Are the AMD FX line of processors fast at folding?

I would think they are the best, are they?

considering they are the fastest processors out there, then yes, they are the fastest. however, until sse2 support for AMD is included (which should be soon), Intel P4's will still outproduce the latest AMD CPU's due to the new QMD packets.

if you haven't already started folding, or if you are and may want a change of pace, join the subteam that i am creating. http://www.ocforums.com/showthread.php?t=377500

In about a year I will buy the absolute fastest FX there is, FX-80 perhaps?

afaik A64 support SSE2, but don't support SSE3 (that should work in E)...
The fastest would be probably 6xx intels, but I'm not sure with that. Still dual cores will own current folding comps. 8xx series or dual core EE, similiar as dual AMDs will be much faster than 6xx or FX. And if we add 64bit system to it and some 64bit F@H in future, difference should be really huge.

With the available WUs, Intels will produce max ppd. For just about anything but folding the FX-55 is the best out there. When, as Frank mentioned, FAH adds AMD SSE2 support to the QMD core, I expect the FX series to again be the king of the folding hill. In the near future, Dual core Intels promise to produce very good ppd (maybe as much as 700 ppd on big WUs) but they are very bandwidth limited. For folding, the Dual Core AMDs are going to be THE killer cpus in single and dual cpu configurations.
Today, the folding performance of the Intel and AMD cpus is close enough that the answer to which is best depends on what WUs are available or folding one or two instances on HT rigs.