I'm a weight weenie too- the problem is with my wallet. So... no Alchemy hubs for me.

I've built several lightweight wheelsets using Kinlin rims. I'm using XR-200s because I'm not a fan of eyeleted rims (though I have one buddy using the "19w" with no problem). And, the 200 saves another 25 grams or so.

I'm doing 20 spoke fronts for up to 150# riders (even though they recommend 24 for over 130#) but it's more about the riding style that makes wheels last.

Being the budget guy I am I'm using hubs from Bike Hub Store. Two reasons- they are inexpensive, and they have a 16:8 drilled rear hub. They are holding up well under a variety of conditions, and most are ridden hard (raced). On the XR200 rim, front- 550g and rear- 700g (CX-Rays and alloy nips.) I like the rear hub drilling, but it requires a center drilled rim like the Kinlin. BTW-Kinlins are some of the most consistently round rims I've seen, and in my price range too.

In a nutshell- I think you can do well with 20 hole front as long as you don't beat the crap out of it. Beat the crap out of it and it won't matter how many spokes you have.

One more thing- all wheels flex. If you can't make 'em flex you ain't going fast enough!