I had no problems at all. Just use the phone number that JWT873 provided and you should be good.
I ended up doing half the activation through the automated person but got stuck at one point and ended up talking to a live person and they basically did the activation for me. I was worried about the ESN of my unit since it was purchased in Canada but I had no problems at all.
I signed up for everything including the Best of XM package and all the channels are there.
Let me know if you need anything else.