Hey, I used the eMac to just try it out. I browsed the web, played some games, and just generaly dicked around with OSX.
I didn't do anything too intensive, but everything I did do ran very smoothly, just as well as my dual 800Mhz, no notsable slowness.
Whatever you get, get the least amount of RAM from Apple, your better off buying your own. Apple WAY overcharges for the stuff.