At $300 for a 500Mhz G3 these are not a very good value in my opinion.
You are still going to have an old iMac with a 15" screen, a tiny hard drive, an out of date video card, a slow CD drive with no burn or DVD ability, and a slow system bus.
Compare that do a new eMac for $799:
1.25GHz PowerPC G4
256MB DDR333 SDRAM
40GB Ultra ATA drive
Here's an older model, refurbished for only $599:http://www.expercom.com/product_deta...DUCT_ID=262340
(appears to be back...