Thanks for the comments so far guys! And to Ley: While I've never really tried the frozen heart on Lux (I suppose I will the next game I play now), I've always thought it was a little not needed on her. The extra mana, and armor are really useful, but remember, I'm going for straight AP pretty much (to a point, then its just not even needed). I've also edited my guide to reflect more on CDR in my build. Between the Ancient Golem buff, your CDR Glyphs, Elixer of Brilliance (after mid game and on) and maybe even your mejai's extra cooldown, hitting the 40% (or close enough that it doesn't make too big of a difference) mark isn't that hard. And the other effect of the Frozen hearth, slowing enemy attack speed, is kinda against how we're supposed to be playing right? :P As to Nashor's....well I plan on trying and AD DPS Lux sometime (for the lulz) and I'll prolly throw that on there just to try it out.

I like it.
Very similar to the way I play her and I've been using her non stop since she came out.
I do like having some extra cool-down reduction though, Frozen Heart 20% CDR, gives some extra survivability and mana which will add some damage to your Archangel's Staff. Nashor's Tooth isn't bad for the 25% cool-down reduction either although you really don't need the extra 50% attack speed but it does add 55 AP and some mana regen so you never have to worry about mana.
I just think that sacrificing a little damage, from an additional Archangel's Staff, for more frequent 'Lazar Beam of Death' (as I like to call it) ends up paying off. Not to forget more frequent stuns and exploding slows.

I have actually had Durandhal on my team before as lux, and oh dear god it's terrifying. (don't lane with him if you're a carry :P he gets the kills and last hits...annoying at times but worth it) i'd recomend paring this lux with a stun like sion or tarric so that you can keep the cc on people and destroy them forever. thi's a great build if you know what you're doing.

+1