It turns out that I videotaped the 2 flights we have made with our Dude,
here is a link to the video of the flights:

http://www.youtube.com/watch?v=J5S8k8ONtgQ

The first flight was on a D12-3 with air in the balloon, the 2nd flight
was on a D12-5 using Helium in the balloon. You can judge for yourself, but
I think that Bob is right, the Helium didn't seem to make much difference.
The altitude was about the same, maybe a little gentler on the landing with Helium.

We had a lot of trouble trying to use the launch pad that comes with the kit
due to the hardness of the desert ground, so we just used a standard launch pad
with 1/4" launch rod both times.

Jeff