Here is some video of our final design for the Minibot. Climb time is slightly less than 4 seconds. Our deploy time is about 1 second. So that gives us a total of 5 seconds. Video of deploying coming soon. We use a 4 way switch to create a feedback loop in the motors to slow the descent. We did find that sometimes the bot would get stuck at the top, so we installed a limit switch to break the feedback loop briefly. Once the minibot drops an inch off the top the feedback loop is enabled again and the minibot comes down nice and slow.
http://www.youtube.com/watch?v=Ac3eQY6dWq8