I've orderd my dual with 1 Gig too but i'll be buying at least another 1 or 2 Gig non Apple ram at half or less the price. I've used non Apple ram in several machines with no problems at all (as long as you follow Apple's specs) After all it's not like Apple make their own ram themsevles anyway.
I'm still waiting for my G5, however I've got 1gb worth of Corsair RAM to stick in there. That's the brand I always used in my PCs...always worked well.
Kingston is my choice. Don't buy it from their website though, retailers such as circuit city and best buy sell it for around 75 bucks for 512mbs with rebates.