We have had great success with the 8020 linear slides in 2005. I would highly recommend them if you are looking for a light-weight, off-the-shelf solution. We used the 6760 (english dimensions) bearings, which proved to be very reliable and smooth over 3 or 4 competitions. I'm sure that many other teams (20 and 222 specifically) will agree with these statements.
I will issue a warning with these 8020 linear slides, be sure to loctite ALL of the screws/bolts in these bearings. The do have a tendency to come loose, which will cause the plastic slide to fall out the bearing. (Not good.) This event has happened to us, as well as a couple other teams. With this quick, and simple fix, you will find that these linear slides are a great product.
You can view pictures of our elevator from 2005
here. Feel free to ask any and all questions.
BEN