I'm using 80/20 with good results.
The only problem buying any extruded aluminum framing is it's weight and if ordered in long pieces ... the cost of shipping (ouch!)
BTW, I'm building a hot wire machine similar to croma and megablock's
I hope to have some pics in the near future on a web site.
I'm also experimenting with 80/20's linear bearings (catalog pgs. 300 - 320)
Anyone have any results/exprience with using them?
They also have wheels that ride in the t-slot.
Here's a link page for various aluminum extrusion supplies
http://www.robotics.com/framing.html