OpenOffice is no speed demon, that's for sure.
You may want to look into optimizing you configuration by turning off services you won't use (ie: apache). There are a few threads floating around here regarding this topic.
I'm using an 800MHz Via C3 (like a K6-II core) micro-ITX board with 256M and the only time I'll say it's slow is when I'm compiling, doing some gimp rendering, or encoding video. It's a great little workstation.