Once you've done it enough, BBQ'ing to feel is much more satisfying and more times than not tastier!
For brisket especially, and maybe butts, I use the internal temp as the first guide, and go by the resistance to the probe as my final deciding factor when to pull it.
However with butts I've found that it's best to always try to smoke that baby to 206 as long as I wrap it well. I have had some odd pork butt cooks where it seems to take too long ~200F where I pull it "early" based upon feel.
Temperature is the hint, but ultimately you want the probe to feel like you're testing butter or a sheet cake. And if you're planning to slice the brisket, you might want it to be just a *bit* more firm than that.