I would enthusiastically join those John has heard giving good reports about the Q-Cut. I bought one a few years ago, and now I wouldn't use any other type. I've never had a single problem parting off a variety of materials, never needed to use a rear tool post. I have since acquired a larger one of similar pattern for my larger lathe, and that one happily parts off under power cross feed (to my great regret I don't have pxf on my S7).
Though the blade design provides a good rigidity, I think it is the tip geometry which is the really crucial factor, it curls the swarf inwards do it never jams in the cut.
The only time I use any other type is when I'm parting off or grooving tiny parts like micro tubing for O gauge work, when an Interstate Mini-Thin set is the dog's b******s (though a bit expensive).
Remember, the quality is enjoyed long after the pain of the price is forgotten.
David
Edited By David Littlewood on 07/08/2013 13:10:57