My HP 1100 printer recently failed and had to be replaced. I therefore have more than a little sympathy for tech support horror, like this little gem:
In 2006, an American soldier in Iraq calls up Hewlett Packard's tech support because he has a printer problem. They tell him that he needs to pay them before they will provide him with information on how to fix it. The soldier is highly dissatisfied with this outcome. The soldier proceeds to express his unhappiness with the product in a very dramatic fashion.
I would never buy or recommend an all-in-one printer, but (at least based on this one review) the HP 5510 should probably move to the bottom of the list if you expect to be working in hot, dry climates far away from tech support. Oh, and don't imagine that HP's regular tech support procedures might change -- although as a result of this incident they now have a policy of free phone support for all overseas military personnel (but presumably only American military personnel).
I remember a time when it was possible to make a blanket assumption that an HP product would be a quality product. That time is past, but here is HP's response to the incident with the soldier. Does it restore your confidence in the company's product line?