I certainly enjoyed The Juniper booth at NANOG 20. I feel that it is important for vendors to bring some of their equipment to the meeting and especially think it's neat if the equipment is doing something. I feel fortunate enough to work for a company that will fly me the vendor HQ to get an in-depth look at the hardware we are doing evaluation on, but not every company is as flush as mine, and not everyone gets the same luxuries. Having the equipment at a meeting like nanog is a good place to get to the people that will actually see and use the equipment. The other "cons" are more apt to draw people that fulfill other purposes.
I certainly like to discuss the vendor's boxes, and tend to do so at the meetings, but it would be nice to walk away with a pen, or screwdriver or shirt. It's a benefit to the vendor as well. Not only do people have to get close enough to grab a shirt, they also end up wearing the shirt and keeps the vendor on their mind.
I certainly want to thank all the vendors that lugged their boxes to NANOG for us to look at. It IS hard work, but it is good to have something physical to point at when talking about it.