To clear up some confusion about the reason so many teams went bipedal:
While my team was demoing the robot at the FIRST booth, I met the president of Team HKU, who took us on a tour of the pits at the DRC. Many of the bipedal robots are derived from the "Atlas" robot, which was designed by DARPA and then purchased ($2mil!!) by many competing teams. They had some open source software but had to generate a ton of their own software, along with hardware modifications to compete in the announced challenges. Therefore, many of the teams ended up focusing their efforts on autonomy rather than hardware construction of humanoid bots.
Of course, a robot purpose-built to carry out the listed challenges would have been much more effective, but these bots served to compete in other similar challenges in previous years (DRC Trials, etc). Of course, teams like NASA JPL decided to design their own purpose-built bots and were very impressive.
Most interesting fact I learned: many of the international teams were unable to order robot parts and have them delivered to Asia (for example, McMasterCarr refuses to ship to Hong Kong/China). This made it especially difficult to troubleshoot and replace broken parts. Thus, many teams brought full Atlas spare robots as a parts source.
Also, the vehicle used in the first challenge could not be shipped internationally, so many international teams were unable to test their bot on the selected vehicle (instead, they opted to have the robot walk the course, leading to an inside joke calling the DRC the "Desert Running Challenge"
Demoing at the DRC was amazing -- we had hundreds of kids (and adults) driving the team's robots from the past couple years. Big thanks to FIRST for coordinating the demo and setting up an entire half-field and even an FMS.
Also, the team got to meet both Dean Kamen and Woody Flowers, who were both strolling around at the event.
