Wow. That is really weird.
I was expecting a little more rhyme and reason to it.
Have you guys tried re-setting the cruise control? I will need to look up the exact process, but from memory it goes something like:
1: Turn the cruise on, then off, on, then off 15 times.
2: Get to the exact speed you want to set the cruise at.
3: Set the cruise and see if it surges.
4: The second it surges, turn it off. Then turn it back on again.
5: Get to the same speed, and set again.
Basically, you keep doing that until it stops that initial big surge when you first set the cruise. I know that I tried it on mine when it first started surging and it really helped, although nothing has fixed it.