well, I'm of the opinion that they can be potentially quite effective indeed, and I like some of them very much... the problem comes with people who do not really understand the "mind muscle" connection, have not been working out for a long time etc, and think that it's just as good to jump on a machine... no, no no... LEARN the FEEL of the bar's the db's, the actual movements... and then, you can move to the machines and really pile the weight on, especially if you don't have the luxury of a training partner... you know the movements, you know exactly what they should be doing and what you should be feeling with them (some HS frames just don't work for some people, as their bodies just aren't quite right with the prealigned grooves), and you can better utilize monster weight safely.