It's definitely slower to actually load pages — I'm guessing that there are still a lot of network optimizations that more mature codebases have accrued that Servo hasn't yet — but holy cow are pages buttery smooth once they do load (and even while they're loading, which is unusual). Comparing Chrome and Servo in terms of UI jank felt pretty shocking, in Servo's favor. Kudos, it looks like Rust and WebRender have paid off.
I have some more involved projects planned for the network stack that aren't yet ready to be picked up though. I suggest working on some bugs above, getting familiar, and then asking in IRC for something in the network stack.
Looking forward to seeing this evolve.