This is the only slimmer I've found, other than one that cuts me off at the waist, that works for me.  I wear a 34DD but have a 26" waist, so any full-length slimmer with a built-in bra is too big for me everywhere but the bust.  I used to buy them, anyway, and take them to be tailored, thus doubling the price.  This slimmer is perfect, as it avoids that annoying line created by half-length slips and allows me to wear my own bra.  The only downsides, really, are that the shoulder straps cut into my armpits a bit (it's tolerable) and the tops of my stockings tend to show if I don't sit just right (I am wearing a knee-length suit skirt, but the garter clips are still kind of low).

I would not recommend this garment for someone who is fairly heavy or has a lot of smoothing to do.  It's kind of thin, which I like, but it doesn't have mega flattening power anywhere.  For someone who just has a small tummy or a little extra on the thighs, it works well to bring that in and make a dress or skirt look more flattering.