By being only half life sized it means the image size on your photo will be half the size of a true 1:1 macro lens. Not too much of a problem for most flowers but if you get into the insect world, you'll soon find you can't get a large enough image to show all the detail.
So far as to using the lens, I have the Sigma 150mm and highly recommend it. I rarely use a tripod but I do use a monopod and just about always use flash. Using flash it's quite possible to hand hold @ 1:1.
As for the comments in that review, the only thing I can think they may have been referring to could be the AF speed, which with most macro lenses tends to be rather slow at times. You soon get used to the way they work though and I generally use manual focus anyway, it give me much more freedom to select the focus point I want rather than the one the camera selects.
Once your into the macro world you could end up like me, totally hooked on it and even 1:1 isn't enough.
