Box joints are very strong once glued because there is so much surface area for the glue to bond to. I think they look good too because the end grain alternating with the regular grain creates a nice pattern.
I'll let you know how my testing goes. If any of you have experience with box joints or box joint jigs, let me know. This one is used in conjuction with a table saw and dado blade or a router table.
This is one option, the WOODSMITH Aluminum Box Joint Jig at Woodcraft.com