The title of this post could be "The companies weren't bad, but their presentations weren't any better."
But I'll go easy. (Hell, I've been guilty too...)
It's not that the presentations were bad, necessarily; well, okay, they were. Yet some had useful information either about the company, the sector, the pain they were addressing, or the solution they proposed. Some even had realistic projections and maybe even a pithy quotable line or two.
Really, I suspect none of the presenters spent sufficient time on their presentations; especially on cutting them. (Wasn't it Pascal who said, he "made this [letter] longer, because I have not had the time to make it shorter"?)
Or thinking through their audiences.
Oh, speaking of audiences: If you're doing a keynote, especially first thing in the morning or just after lunch, do something different. Use your OWN knowledge of the topic to craft your points and don't really on someone's data points or best-selling book to get your message across.
And don't assume that the audience either knows too little or too much about your topic. (Especially after you've ask them who they are. If you're going to ask, you need to adjust accordingly.)
Paul Kedrosky posted some good tips for better presentations (or at least quirkier ones), which has my vote: paulkedrosky.com
And, of course, there is always something worth reading at Presentation Zen.
Before you commit a presentation misdemeanor, consider the alternatives. And respect your audience.