For current Mac fans, that's good. For PC fans, though, there's not enough new to make them switch. The heart of the iMac is an admittedly speedy 233 mhz G3 processor, but you could buy a Macintosh with the same clock speed and processor months before the new machine was ready for public consumption. This is a good thing, but precious little software is available on the Macintosh platform besides graphic imaging tools that can use the G3's prowess. Ditto for the 4 gigabytes of hard drive space.
Larger drives are already common and cheap.
Those features offered are really not bad for a consumer-level machine you can probably find in a few months for a much lower street price. Most notably, the iMac has no floppy drive. That means no more 3.5-inch disks. Although we've been needing to find a better storage solution than standard floppies for some time now, not everyone has access to a ZIP drive or similar media. That means if you already own a Mac, your old peripherals may not work with the iMac unless you buy an adapter - and in some cases, appropriate ones aren't available yet.