Bruce is right. Wood conditioner is made for, and only should be used for soft, pourous woods. I have used it extensively on knotty and clear pine, such as plank floors and bargain unfinished furniture and it has helped me make these items look world class, instead of just looking like (ho hum) "stained pine". I have also used it on butternut, which has parts of the grain that are EXTREMELY absorbent and it has evened out the staining colors enormously. A true test should be on soft wood that has areas that would otherwise absorb too much stain, like around where large limbs coming off the tree causes a change in grain direction, usually with a larg swirl grain around the area. Stain colors definitely need to be experimented with and adjusted significantly darker to compensate for the conditioner taking up some of the absorbtion potential.
You DEFINITELY have to read and follow the directions with this stuff, and I find that you need to wipe up any excess fairly quickly or it gets a little difficult. If you don't believe me, see the source: http://www.minwax.com/produse/prestain/pupswc1.htm