When You just log on to the game, it stutters a bit for the first few minutes. Every time a new person comes into view there's a small pause when the graphics are loaded. After a few minutes it runs pretty smooth because all the graphics has loaded. And some modem users even get disconnected if they happen to run past a mob during the first few seconds because of this loading pause.
SUGGESTION: Make an option to load it ALL at startup! Of course this is only for the people with LOTS of memory. But then again, memory is very cheap these days. And I think it could really save the game for those modem users. Being a former programmer myself, I even think it's a pretty easy thing to do. You just load all the stuff, using the code that is already there for it. That shouldn't take more than a few minutes to code for an experienced programmer