Keyword stuffing as you call it, isn't a good idea in my opinion as not only does it look unnatural, Google are also clamping down on it and they will rank your page lower than the rest if it's blatantly obvious your using SEI techniques in that way.
I'm sure we've all read an article that we have noticed the same few words being used time and time again, to the point were it's almost unreadable.
If we can notice it, you can bet that Google notice it also.