I've noticed that most of the opinions here tend to align precisely with my own, which is gratifying, because it's evidence that my thinking makes sense. However, it's also irritating, because it means I learn less and I have little to contribute.

I noticed this as well, while first reading the sequences. I flew through blog posts, absorbing it all in, since it all either matched my own thoughts, or were so similar that it hardly took effort to comprehend. But I struggled to find anything original to say, which was part of why I initially didn't bother making an account - I didn't want to simply express agreement every time. (And now I notice that my second comment is precisely that.)

Biggest upside: Lesswrong has it's own, rationality/philosophy specific jargon, which is really helpful for communicating complicated ideas using very few words.

That's one of the things I've frequently benefited from in my thinking. I have found that the concepts behind keywords like dissolving the question, mysterious answers, map and territory, and the teacher's password can be applied in so many areas, and that having the arsenal to use them makes it much easier to think clearly about otherwise elusive concepts.