Yes, it’s slower than old-LessWrong. When we rewrote, we built on a collection of libraries and frameworks which were… not exactly production-ready. This has required a lot of compensatory engineering work to bring performance up to par, and there’s still a bunch more compensatory engineering work left to do.
In the few months immediately after the rewrite, it was catastrophically slow, to the point where if you opened a bunch of sequence-posts quickly in new tabs, whichever server from the pool handled the requests would die. It’s much better than that now, but it’s still not where I want it to be. When it is as fast as I’d like, I plan to write a long post with technical details of what we had to change. In the mean time, yes, we know and we’re working on it.