Javascript doesn't slow down a computer, unless it's badly written and causes an infinite loop (or extrememly long loop) or something
I'd have preferred no javascript at all, same reasons as Bleys mentioned, as it can be easily abused to do undesirable effects.
But I guess if it's not going to be intrusive (like autoredirecting) or destructive (messing up the rendered page layout), or anything else which can be annoying, I suppose it could be done very discretely (roll over links, as one example)Rollovers that change text fonts or size, however, isn't good as it can mess up the layout in some browsers as they try to re-render everything around the new formatting on the fly.
