As I understand it, a lot of pieces critical for real world use are really just minimum viable implementations to allow Servo to work end-to-end and feed data into the interesting parts. In particular, things like the network stack don't benefit nearly as much from aggressive parallelism and so little effort has been focused on them, not even bringing them up to level with the techniques other browsers use.
Thanks, I can understand how that might be the case (that many parts are MVIs, as you said). My issues were never with things like networking, it was more that scrolling was really bad, and stuff rendered slowly.
WebRender has matured a lot lately; it's even in Firefox nightlies behind an about:config preference. That said, there are still rough edges. If you see rendering slowness, feel free to file issues on http://github.com/servo/webrender.
There are no silver bullets for performance, only lots of lead bullets. I'm confident that parallelism via GPU and multicore is a large architectural win. But lots of making the Web fast involves a ton of little special case optimizations that just need to be implemented. That's how Stylo went: promising benchmarks and a mediocre user experience at the research stage turned into great benchmarks and a great user experience with production engineering work.
