What's the latest and greatest extruder?

This last week I've been making great progress on my Darwin, thanks to the excellent Reprap instructions, Ian's cast parts kit, and the awesome folks at Interaccess for loaning me some workshop space. Got the Z axis almost finished, just need to splice that belt and test it out.

I'm thinking ahead to feeding the extruder - from Nophead's progress, it looks like ABS is the way to go. ABS is certainly my favorite plastic, as I spent a third of my life careening down mountain streams in ABS boats, so ABS holds a special place in my heart. At least as much as a plastic can earn a place in one's heart.

Anyway, what's the state of the art on the extruder? I see Nophead's got closed loop control on his extruder motor - that seems essential, is there a page somewhere that describes Nophead's encoder setup?

Also, any other tips on running ABS in the extruder? Or should I be using some other plastic to start?

Thanks!