As Barbara mentioned, I think it all depends on what you are looking for in terms of your writing career. Ive looked into it on several occassions and it is not exactly what I need. I feel that a lot of the information offered, I can find in other places like for example on the write4kids website, and it[s a lot cheaper to join. They have very valuable info if you are looking for information on the trade and on writing things like chapter books, easy readers, ESL books, picture books, things that have to do with elementary school curricula, which is a big part of what scbwi offers too. SCBWI is also big on literary works and trying to strive for newberrys or any other kind of prize. One of the cool things they offer is chats with authors and illustrators. Where am I going with this...not so good a place if you are trying to write something very commercial.
At some point they allowed me to visit their boards and there was a lot of action going on//a lot of people are on the boards which is cool but there are also a lot of newbies, so again, it depends on what you are looking for and where you are as a writer. At some point there were famouse writers on the boards giving advice, but not anymore.
I also had the opportunity to visit the UK version SCBWI British Isles and to be honest, I liked it a lot more! They are very well connected with agents who kindly give their time to actually talk to new writers. It looks like they are more inclined to writing both commercial work as well as literary. I got some good feedback from 2 agents after I was allowed to particiate in one of their contests.
There seems to be a lot of fun stuff going on and they have some freebies that are cool too. They were even willing to take me as a member even though I live in Mexico! I recommend you check them out on twitter and their webpage where you can sign up to get their free online magazine.
British Isles | SCBWI British Isles
If you do decide to join, I suggest you do so in the country where you are looking to publish. Each country is different when it comes to publishing. In Mexico for example, they are very active within the literary scene.