I use an HP Photosmart 4750 printer with Mac OSX 10.6.8. Since the latest software update, (HP Printer Driver Patch v1.0.0) performance is awful. After a document is printed, it stays in the printer queue for a long time, which delays printing of any other documents also queued up.
If I manually delete the already-printed document, the next one will print sooner... but this shouldn't be necessary, of course.
The previous drivers wouldn't always wake the printer up when you sent it a job, and that issue seems to be resolved. But this isn't really an improvement.