General tip: If HN is being laggy and you're determined you want to waste some time here, open it in a private window. HN works extremely quickly if it doesn't know who you are.
I guess there does exist many alternative UIs, though I don't see many that support commenting. I wonder if the "API" (if there's any) allows for that, or if people are just scraping the page and reformating it.
There’s plenty of stuff I’d like to be different about usability of this site, but perf is basically at the bottom of that list.
The cache is faster because its not having to talk to the database, and can be done at by the load balancing layers rather then the actual application layer.
Wikipedia does this too (although, via a layer to add back on the ip talkpage header).