But now you've got me nervous about the H-P proprietary drivers. Need I be concerned about that?
Not really, but it helps to understand the difference. Mac OS X includes a slew of drivers, from a standard set to the current crop of drivers from printer manufacturers like HP. The HP drivers may be proprietary, but they are freely available to all users. In addition to including these 3rd party drivers in Mac OS X, Apple regularly provides driver updates whenever the printer manufacturers make them available.
The difference with the standard drivers is that in this case HP, not Apple, makes those drivers, and that the end user (you) may have to wait for HP to include certain functionality or fix bugs in an updater, rather than for Apple to do so. That said, there usually is no problem with using printer-specific non-standard drivers.