When I first read the new iMac G5's were using DDR 2 DIMMs it sounded very exciting. Then I found out that the stock 512 RAM is not replaceable. and that there is only one additional RAM expanson slot. This presents a costly problem to anyone needing 2 GB's of RAM to cover their work. If you need more that 1.5 GB RAM, your only alternative is to buy a single 2 GB stick, adding it to the stock RAM for a total of 2.5 GB's That sounds fine until you see the current prices on SINGLE 2GB DDR2 240 pin, CAS 4, PC2-4200 1.8volt, Non ECC, Unbuffered upgrade DIMMS ONLY $909.00 on sale at Crucial. Module Details: CT25672AB53E Part Number: CT25672AB53E Module Size: 2GB Package: 240-pin DIMM Feature: DDR2 PC2-4200 Configuration: 256Meg x 72 DIMM Type: REGISTERED Error Checking: ECC Speed: DDR2-533 Voltage: 1.8V Memory Timings: CL=4 Specs: DDR2 PC2-4200 CL=4 REGISTERED ECC DDR2-533 1.8V 256Meg x 72 US $1010.99 Save: $101.10 Sale Price: US $909.89 (This was Crucial's only listed price for a single 2 GB module meeting or exceeding Mac specs) And $399.00 at OWC macsales.com 2.0GB (2048MB) PC4200 DDR2 533MHz 240 Pin DIMM Module for Apple iMac G5/1.9GHz and 2.1GHz Models only. New w/LifeTime Warranty. (OWC4200DDR2M2GB) $399.00 Even with OWC's remarkable price on single 2 GB modules, you're paying twice the cost for slower CAS 4, 2 GB's of RAM when compared to any other current Mac model using DDR SDRAM single 1 GB modules. This will be an important consideration for buyers looking at PowerBook updates as well.