My first generation G5 iMac is fairly easy to open. A few screws on the bottom, and the back pops off.
I can't find instructions on opening the new 24" iMac. I'm about to buy one, and I'm wondering if it will be easy enough for me to open it up and replace the hard drive, or if I should just do BTO and buy the bigger drive from Apple. Anybody know where to find instructions on opening the new iMac, and is the hard drive easy to replace?