babies & sign language

I got this really neat sign laguage book for infants when Taden was born and really wanted to teach him a lot of words to help us be able to communicate before he actually learned to talk. The book suggested starting it around 9 or 10 months (if I remember right?) but I was anxious to start ASAP and began when Taden was only about 6 months old. I definitly started too early though and didn't remain consistant. After some time, he learned to sign "eat" which was super exciting, I tried the word "milk" but we still haven't mastered that one. Recently we tried "please" and "thankyou" and he caught on right away! We've been working on "all done" and I'd like to try "more" again. We worked on it for a while, but didn't keep at it. I'm curious what opinions might be out there regarding sign language for babies. I recently heard of a little boy who hardly even talked b/c they had taught the little boy so many words in sign language, that that was how he continued to communicate, even when he reached an age where he could have started to talk. I suppose, like with everything in life, it's good to have a balance. Personally, I'm in favor of teaching babies to sign, it's a wonderful way to communicate and figure out what baby wants, prior to them being able to verbally ask for what they want. But, I can also see how it would be wise to watch and be sure that it doesn't become their ONLY way of communicating once they reach the age where they should be talking. Another great resource for teaching infant sign language is the baby einstein DVD (thanks Dan and Laura!) - it's very easy to follow and has puppets in it - definitly keeps baby's attention.