We have used this for light and reliable slide/lift mechanisms for the past 2 seasons. Now we are flipping over to lots of Rev Robotics parts to build strong and light robot frames as well.
For smaller applications the REV Building System also comes in a 15mm x 15mm square extrusion. The slots are designed to fit standard M3 hardware rather than expensive t-nuts.
NOTE: we make two different size extrusions and the plates and brackets for each one are not directly compatible. Please be sure that you are buying the right bracket for the correct system when purchasing. The systems will either be marked 15mm or 1 inch.