One of Booklab's faculty authors returned from a recent conference with feedback on how his pre-conference preparation went. He viewed the university press booths completely differently based on discussions we had about publisher lists. One of the presses had been courting him, and he was able to see what else they published in his field, look at the actual books, and speak to an editor.
One of the advantages to going to the booth at your professional association's big annual meeting rather than just looking at catalogues is specialization. The press will go out of its way to identify itself to you and your colleagues in terms of your specialty. Also, book are expensive and time-consuming to gather (most libraries won't have all of them), so you'll be able to go through many of them all at once and make more informed decisions about the suitability of a particular publisher for your work. Imagine how much easier it will be to create a targeted prospectus with this kind of understanding.