I'll second that. I used one for about three years with Windows Server 2008, primarily as a NAS and for playing around with Windows domains. Cost me less than £100 (plus HDDs), held five 1.5TB hard drives, ran near silent, and was reliable.
I've also got a HP PSC1215 scanner/printer that is over a decade old and still works fine. I can't really speak to the overall quality of HP gear, but the few pieces of hardware I've used from them have been pretty solid.
Their storage is a good value for the money too.
If you want to talk enterprise, the NonStop Integrity platform is as reliable as z/OS. That's real niche though.
That's about it though.
Their enterprise software is as bad as CA. They aren't really innovating anything interesting.
Do you count Agilent products as HP? Probably not, but if so they make a bunch of pretty solid instruments. And arguably the name "HP" should be associated with the entity that today we call "Agilent."
The ProLiant micro servers are pretty good for a home / small office environment.
Also, we have three managed 24/48 port switches at work that have not given me any grief.
(We also have an EliteBook 17" notebook that for its price of ~ €1700 should totally kick ass but instead seems to be the slowest notebook in the entire company. All in all, HP notebooks seem to be more trouble than their counterparts from, say, Lenovo or Dell.)
I bought a 28S in 1989 or 1990 and it's still working. Last year I saw the HP 35s and bought one. I'm still using the 28S even though my battery door is broken as is some of the plastic around the battery door.
The 35s is soooo close to being a great device, but a few things drive me nuts.
For those of us that just have to have a web server in our bedrooms.