Linear Slide suggestions welcome

[domar]

Hi all
I am still at the accumulating parts and ideas stage. I am wanting to build a cnc router table with stepper motors not servo's. I have two questions for which [I] am seeking advice or experience from others who have gone before me.
1. I want to make my linear slides with skate bearings running on 6mmx100mm rail on each side. I would like to use aluminium for the rails but I am not sure how it will stand up to use. I could use steel but I like the idea of al as it is easier to work and there are no problems with rust. Also the rate of thermal expansion will be the same as the frame to which it will be bolted.
Has anyone used aluminium in this sort of situation???

2. I am considering using fixed lead screws and driven nuts. I believe this should have two advantages.
a. Less inertia as only turning the nut and a pulley rather than the weight of the leadscrew.
b. No problems with whipping of the lead screw at higher speeds.

Any comments welcome.

domar