I bought several NX series HPs instead of Dells late last year for some of our interns. They took the beatings rather well, and no major complaints. One shipped with a bum battery, though that's happend to us with Dell before too.
Really, I've seen the business class HPs in person, and I am impressed. They are very nicely built and have a solid feel to them. Even thier desktop models look fairly durable. I also know some people who say "never get an HP," but they are the same people who go and buy a cheap Dell. Ultimately, I trust HP's build quality, at least as much as the next guy's. I think HP's business notebooks have 3 year warranties, but I could be mistaken.