Message in a bottle: stainless steel, aluminum or plastic?

Catherine’s posting about Nalgene bottles actually inspired me to look into the whole water bottle business. I heard from a biologist once, years ago, that Nalgene bottles leech carcinogenic chemicals and shouldn’t be used. I never got one. Then again, I already have cancer so what do I have to worry about!

Yesterday, I decided I wanted to get a reusable stainless steel bottle. I did some research online and found out that people are essentially split between Klean Kanteen fans and SIGG fans. Whereas KK is made out of just steel, SIGG has aluminum lining, if I understand it correctly.

My question is, is aluminum honestly better for you than plastic? Sounds pretty scary to me. I remember when anything made out of aluminum was an absolute no no. Any bottle experts out there?