I've been running Windows 7 for a few months and I've just installed it on my wife's computer, too.
I've set up a Home Group network, via our wireless router, so we can share the HP Photosmart C4180 that's attached via USB to my computer.
Everything works fine, except for one oddity. When my wife's computer is first switched on (with mine already on), if she tries to print out an email from her Windows Live Mail, it takes ages for the printout to appear.
Sometimes there can be around 6 or 7 minutes between clicking 'Print' and the printout appearing on the printer.
After this initial delayed one, all printouts from her computer only take seconds to appear on the printer - it's only this first one that's so slow, and only when it's sent from Windows Live Mail. Word documents always print immediately.
I've ensured that the delay is nothing to do with my computer being asleep, or the print queue being busy.