for those that use the 4.0.0c client, there are a couple of things you can do that may improve your experience with it.
I've experienced some client lag, strange discoloration around the edges of the screen at times and so on. I'm using AOS, by the way.
I edited uo.cfg and turned off the translation server, ie:
TranslationServer=off
TranslationServerAutomatic=off
I also thought "what the heck" after reading about OSI's patch to the 4.0.0c client that was supposed to plug a supposed memory leak. I ran uopatch and the patch took just a few seconds.
So far tonight, the client seems faster and "cleaner". The process takes an average of 9,486K memory usage and runs about 10% cpu usage.