long answer: there are pros and cons of each.
short answer: YES
While I still use bolts for super high shear areas, 90 percent of the fasteners we used last year were rivets. Our entire robot was essentially 1/4" aluminum rivets, 1x1x1/16 aluminum tubing, and 4"x4" aluminum triangles for corner connections. We never had a rivet fail. Removal is easy as pie too, just drill through. Hole enlargement was minimal in my experience since the center of the rivet kept the bit straight.
I think someone said earlier that a team could dissassemble and reassemble a robot faster using rivets than bolts. I have to agree, you just have to drill through and re-rivet. I also hate having to tighten loose nuts so riveting is definitely my favorite.
-Vivek
EDIT: With a good square, you can get perfect 90 degree angles without machined corner braces. We just cut them on a miter saw and clamped everything down to a work bench and lined it up with a square. Make sure your holes are aligned though.
EDIT2: We probably saved a few pounds by using rivets too. They are SOO much easier to maintain. Sorry about the edits, I just really love rivets.
