Thanks for the detailed reply ElectronDF!

I'm quite enjoying the shammies at the moment (level 17). A couple of things I've noticed are...

1. I've got Heirloom items equipped on the shammie on my account, and the 20% heirloom XP bonus DOES stack with the refer-a-friend bonus, so he's getting a lot more XP than the char on the other account.

2. I've now bought 4 Warcraft accounts over the years and every single time I pay for one, I have to wait 48 hours before the trial account restrictions are removed, which is very annoying. I can't trade money, bags or items to the new account, or use the AH, whisper, etc.