The UTD offer is only good for 90 days after you buy your computer so I don't see any logic in waiting. Yes, the UTDs may come w/ 10.6.1 in 90 day, but maybe not. It would depend on how many 10.6. discs Apple initially ordered and whether it meets its distribution expectations. Regardless the update will always be available via d/l so no real read to wait.
Also, one of your "issues," the lack of a driver for your printer, is controlled by HP. Apple won't include the driver unless HP gives it to them. I'd contact HP and ask if they intent to support your printer. My guess is that the list of supported printers now, is THE list of supported printers, except for new products released today and after.