We've have one 1G stick in our eMac 1.42G for over a year along with one of the original 256MB sticks. Runs like a champ and, if all goes well, I'll drop in another 1G stick this fall. I bought my 1Gigger from OWC--no problems
Hobo is right--Apple won't update machine specs when larger compatible RAM modules appear. In the older spec format, they sometimes acknowledged their existence but usually in a very equivocal way: "Compatible modules up to XXXMB may be available but have not been tested." With the new tech sheet formats, there is nothing.
One reason I don't buy Mac RAM from Crucial is that they follow Apple specs to the letter, leaving upgradeable machines like the USB 2.0 eMacs behind. See this:
eMac 1.42G RAM at Crucial
That means to find a compatible 1G module for an eMac on their site, you have to figure out what other Macs can use that module and find the listing for it. That can lead a novice RAM buyer to the wrong product. Compare that to listings from my favorite online Mac RAM vendors:
eMac 1.42G RAM at Data Memory Systems
and
eMac 1.42G RAM at Other World Computing