I think it's clear that the "consumer gadget" category and "video game" category warrant sites of their own. I understand Jeff/Joel have concerns with a proliferation of sites ("Knitting Overflow") - but it's not hard to imagine the business model for SO/SF/SU scaling nicely to other sites and completely different audiences. Each with their own eyeballs and ad opportunities.

The video game site seems like a no-brainer... with games, platforms, and hardware devices as tags (not to mention things like "cheat", "walkthrough", "easteregg"), lots of opportunity for badge challenges, etc... with fall/winter being the time that a lot of new games arrive (particularly for consoles), the timing seems good as well.

The gadget site may not be as clear because the category is so broad. Digital cameras. PDA/phone devices. Entertainment/media devices... even "smart dishwasher".... so it's possible that a gadget site gets unwieldy and you end up with people asking for a "photography" site, a "mobile device" site, etc.

But even with the possibility for gadgets getting very broad very quickly, I think both sites are worth doing.