Your feet will stay dry in you step in puddles, etc. that are below the tops of your shoes.
What's not so good:
If you have to step in water above your ankles, your feet will get wet and stay wet because the Gortex will hold the water in. I have an old pair of Hurricane Ridges that I keep primarily to remind me that Gortex, despite its advantages in other areas, is not suitable for hiking shoes, in out out.
Far better (and cheaper) during winter months, is a pair of grocery or newspaper bags, which you can rubber band to your calves for deep river crossings. In warmer months, use a pair of shoes that dry fast (like Vibrams or Propet Walkers), and just wade right in.
Just my two cents, but the one thing you need to protect above all when BPing is your feet. Gortex just doesn't do the job.