In answer to your question blue moon, I think the benefits of baby sign is that it allows them to say words they could not say verbally. To explain, I have not bothered to teach the signs for simple words like mama, dada, baba etc beacuse dd can say them. However, I have taught her signs for words she couldn't say in a month of sundays, like washing machine, ceiling fan, windmill and chickens or other things she likes to see! Personally, I feel that baby sign should supplement verbal language... but for me it is not about making her a superbaby or anythging like that, but it is about making her happier.
To give you an example, dd knows the signs windmill, book, and various other toys. If she wants a specific toy to play with, she can sign that toy, we do not have to rely on guesswork and pointing! So she gets less fustrated and we have a clearer idea of what she wants. After all, she could never verbally ask for a windmill... her vocab is nowhere near that good yet. The two work together in my eyes!
Secondly, as for the pain thing... no she can't say where the pain is... but she can say pain. Add in a bit of commonsense (if she's teething, a sachet, if she's hot some calpol etc!) and we can work it out quite quickly. I do find that you generally know when they're unwell, but I have found it very helpful when she's teething, as its very difficult to know otherwise.
Finally, just a little example from today... We had a big trip out Xmas shopping... On our route we came across some fish. DD saw them (I didn't)and signed fish so I took her over to see them. We stopped for a few minutes whilst she looked at the fish. Meanwhile, I saw a baby slightly older than DD being pushed by, who was pointing at the fish and whinging. Mum was oblivious to what it was her dd wanted and tried to pacify her but kept on walking. Baby kept on whinging out of sight. I felt so sorry for that little girl... she wanted to see the fish, but mum didn't know what it was her dd wanted and so the little girl missed out. DD had a further three visits to the fish, all because she could sign rather than just point!
And finally, no signing is not the be all and end all answer to all of your problems, but I don't think it pretends to be. However, if you read any toddler books, whenever they mention toddler tantrums, they all say that often some tantrums are connected to a child's inability to communicate sufficiently for their needs and desires. If signing can help reduce just those tantrums by say 10%, then that's 10% my life is happier and that of my DD! I don't anticipate that it will stop all tantrums... if now is anything to go by, she'll be quite a madam, but I am hoping that it may ease some of the fustration that so many toddlers at that age feel (and boy I know this as I have a friend who's child was a head banger, wooden floors the lot. When she took him to the HV about it, she was told there it was beacuse he did have quite limited language skills and was getting fustrated!) So If I can do anything to help me avoid just some of that I will!
And thus ends another thesis ;-)