Hello, I'm an undergrad student who's been reading LW for about six months now. So far I've stuck to lurking for a couple of reasons. For one thing, most of the comments I have are already made by other people. Also, there's enough information on LW that it seems more fruitful to move on to a new article than to post a question.
There's a LOT of background reading available here on LW, which is intimidating to a new reader. I can say for myself that it's difficult to bring myself to post when I know there are dozens of background articles I still need to read. That's probably a good thing, though -- from what I've read about SL4 (and what I read in my brief forays there), LW has avoided a lot of the redundancy and conversational looping that its predecessor had.
Some research says that lurkers make up over 90% of online groups. I suspect that Less Wrong has an even higher percentage of lurkers than other online communities.
Please post a comment in this thread saying "Hi." You can say more if you want, but just posting "Hi" is good for a guaranteed free point of karma.
Also see the introduction thread.