In general, if it’s not a pipe that I avoid, then it’s a good smoker. All of the factors previously mentioned by others here do come into play, but there are indeed pipes in my collection that I avoid, despite their uniqueness or eye pleasing appearance.
If a pipe tends to be a wet smoker regardless of what I put in it, or if it has a rather obstinate draw no matter how much I clean or ream the draft, it will fall into the “skip it for now” category and generally not get as much attention.
Fortunately, I don’t have many that fall under that description, except perhaps a few novelty pipes and a couple of “basket pipes.”