I don't think it's so much that they used their own OS, as they used an OS that did not include many of the basic functions that Android and Apple users take for granted. Putting out hardware based on a feature-starved OS that was essentially crippleware was not a smart move.
That was as bad a debacle as the RIMM tablet. Let me add from personal experience HP Laptops are crap. One died because the motherboard “melted”, a common problem with the model I had, and the other one I owe works but you can hear the cooling fan reeving up all the time.
I've had terrible experiences with HP desktops and laptops alike. One laptop used an Nvidia chip that needed to be compressed with several heat-resistant faucet washers sandwiched between the keyboard cover and the motherboard in order for the chip to make contact with the motherboard - a post-warranty repair dreamed up by some enterprising end user. This was supposedly a business class laptop.
Their printers are crap as well. I talked to a guy who repairs printers exclusively. Been in the biz for quite some time now. He disclosed that HP started using craptacular systemboards from Malaysia about 4-5 years ago. HP printers USED to be rock solid. I’ve had ‘em bad right out of the box.