Thats notmuch of a performance jump. The AMD will be faster, but I doubt it will be that noticeable. I guess your power bill will go down since P IV's are power hungry.
Buy at least an AMD 64 (It has a more effiecient memory bus), or if you can, get an Intel core duo which is the performance king right now. It's weird saying Intel is the faster CPU since it's been so long, but they are with Core Duo.
-S