Actually, last year Twitter launched a JavaScript-heavy rewrite that was much slower to load and interact with than it was previously. It seems to have improved since then, but at the time it was fairly tiresome to use.
It's a bit bare-bones, but IMO totally makes up for it in raw plain-HTML speed.
I use twirssi myself, but a common complaint I've heard of the twitter site istself is that its auto-refresh will destroy work-in-progress tweets.
(The 140 char limit can lead to serious time spent crafting responses without resorting 2dis typ o stf)
I just timed it: after turning off the wifi, clicking my bookmark of a saved twitter search on a Nexus S took 10 seconds before it showed the centered twitter logo (presumably that ajaxes in the rest of the page?) and another two or three before showing search results.
Frequently it's long enough that my phone turns off the screen while I'm waiting for it to load, at which point I usually give up.
(Yes, this is the wrong place to complain. I am only a very casual consumer of twitter -- don't even have an account myself -- so I don't know the appropriate tech support channel. Perhaps because of my casual usage they in fact would prefer to discourage users like me.)
I'm talking about the app, not the page, of course.
